tao teh ching 59

In caring for others and serving heaven,
There is nothing like using restraint.
Restraint begins with giving up one's own ideas.
This depends on Virtue gathered in the past[1].
If there is a good store of Virtue, then nothing is impossible.
If nothing is impossible, then there are no limits.
If a man knows no limits, he is fit to be the ruler[2].
The mother principle of ruling holds good for a long time.
This is called having deep roots and a firm foundation,
The Tao of long life and eternal vision[3].

[1] Lau has:

It is because he is sparing
That he may be said to follow the way from the start;
Following the way from the start he may be said to accumulate an abundance of virtue...

[2] Lau suggests that no–one knows his virtue.
[3] Lau has:

When he possesses the mother of the state
He can then endure.
This is called 'the way of deep roots and firm stems' by which one lives to see many days.

The Ma wang tui text is different enough from and both similar enough to one or another at various points, too, to warrant being reproduced here in its entirety:

For ordering humanity and serving Heaven, nothing is so good as being sparing.
For only if you are sparing to you can you, because of this, early submit to the Way.
Early submission — this is called 'to repeatedly accumulate Virtue'.
If you repeatedly accumulate Virtue, there is nothing you can't overcome.
When there's nothing you can't overcome, no–one knows where it will end.
When no–one knows where it will end, you can possess the state..
And when you possess the mother of the state, you can last a very long time.
This is called having deep roots and a firm base.
It is the Way of long life and long–lasting vision.

Wang Pi says:

Se (husbandry) refers to the farmer. The farmer puts his farm in order by bringing uniformity to it by earnestly ridding it of weeds. Its naturalness is fulfilled by his preventing the threat of its damage by neglect, which is to say, eliminating the cause of such damage (the weeds). For receiving the mandate of Heaven above and keeping the people content below, nothing surpasses this.
'Quick submission' is to constancy.
Allow repetitive accumulation of virtue to happen, and avoid forcing the people to hasten. Only thus can you have them submit to the way of constancy.
Tao is infinite.
If one attempts to rule a state while limited by constraints, one will certainly not keep that state.
That which keeps a state at peace is called its mother. The 'repetitive accumulation of virtue' means simply that , having carefully planned the roots as one's first consideration, one then goes on to tend to the branch tips. This is what enables one to live one's live to its full and is referred to as 'having deep roots firmly established', for it is the Tao of long life and enduring insight.

Cheng says (in part): 'To acquire the habit early' is to practice at every opportunity... To be 'deeply rooted and firmly seated' in that place described as the Mother (the Mysterious Female), is to have 'longevity and lasting vision'.

Compassion, which is the manifest energy of insight (so much so that, if one's insight does not give immediate and equal rise to compassion, it does not merit the name insight), arises based on virtue — accumulated virtue — the 'habit acquired early through learning to put it into practice at every opportunity'. Compassion is not being all lovey–dovey and sweet; compassion is getting down next to the diggers in the cess–pit, picking up your own spade and putting your back into it... It is realising we're all in the same boat and doing what you can to make the voyage both meaningful and easy. This often entails setting off in some very odd directions, but, since 'the bodhisattva is one who gives rise to a mind that is unsupported anywhere' as the Diamond Sutra says, one has no particular end in view except to make life easier for one's fellow beings, and — if it's at all possible — even somewhat meaningful.
'Restraint' — good husbandry — is not having set ends in view... The situation is sufficient in itself; just help. And 'filling up wells with snow' is pretty much what we will have to spend much of our time doing...
Eventually people work it out for themselves... as do we. Then they move on to something else — very often another well, unfortunately... As do we.

Unfortunately.

Helping without imposing one's own 'better way' (as in: 'Be reasonable — Do it my way')... Not so easy...
One also tends to forget, when passing on one's 'wisdom', that it took one years and billions of repetitions to even begin to work out.

Just help where help is needed, share pleasure where pleasure is possible, put your shoulder to the wheel when it needs a shoulder to the wheel.

It is, of course, also true and many Taoist practitioners, following Ho–shang Kung, see this 'restraint' as the practice of conserving semen and the life breath, there now being a large number of texts in the Taoist (and Tibetan Buddhist and Shaivite) Cannon referring to and/or detailing such practices.
The problem with them is that — unless one is very careful — they seem to assume the reality of duality.
There's a lot of whacky bullshit written about Taoist and Tantrik sex, but, from the little I've been taught about it, I don't think many people would be up to the actual practices involved — practices which have almost nothing to do with the seeking of 'pleasure', and, indeed, some of which are quite 'vampirish'.
The Taoist religion is a vast phenomenon, ranging from out–and–out shamanism with its practices of attack and defence, trance and divination, on the one hand, all the way up to the furthest flights of human philosophy — openness, voidness and compassion — on the other.
Taoists of some schools do , indeed, practice a 'dual cultivation' which always seems to me rather cold and calculating. Shaivite and Taoist 'dual cultivation' seem to be based in the practitioner and the needs of the practitioner, whereas Buddhist practices are based in compassion and wisdom and the needs of compassion and wisdom...
It's a vast subject and I don't really want to go into it, so a single comparison will have to suffice: In Shiva Tantra, the practitioner is Shiva and the universe, his partner included, is his emanated energy — shakti. The practice, then, is to realise that Shiva and shakti are one and then withdraw shakti back into Shiva so as to realise the ultimate. In Buddhist tantra, the female partner is wisdom and the male skilful means. The skilful means seeks adequate response to the solicitations of wisdom and the energy thus generated is shared and dissolved as the manifestation of bliss–emptiness.
The practices entailed are extremely difficult and 'laborious' — not so much in the actual practices themselves, but certainly in the length of time (18 hours a day for months and even years on end?) one is expected to dedicate to it. These practices are also extremely carefully monitored by the teacher, who will check into the retreat centre at least daily to make sure that one is not creating subtle attachment. It's very much a question of using poison to fight poison, but... as I said above... this needs to assume the actual existence of poison, does it not?
Taoist alchemy, much like its Western counterpart, also finally developed a school of thought wherein all alchemical practices came to be viewed as internal and symbolic and several schools of Taoism then branched out from this idea. My personal opinion (and this is not to denigrate or look down on any of the other approaches, all of which, it seems to me, have their place and are a very real motor along the path, each at its proper time) is that — since such schools embody, embrace and then transform into openness all that comes before them — they are somewhat subtler, somewhat closer to the ultimate nature of reality...