Know Thyself. Cliched, but true, that good advice doesn't quite capture the full importance of knowing oneself. A former covenmate of mine formulated the advice a little differently, and I think it communicates much more clearly:

Be ruthless in knowing yourself.

Question yourself. Don't let questioning paralyze you, but examine your beliefs, your motives, your desires, everything. If you come up with an answer, run with it, but question again even as you move. You will spend more time learning about yourself than any theology, any magickal skill, any craft.

Be ruthless in knowing yourself.

It bears repeating. The Rede advises to "Do As You Will." How can you Do something if you do not know what it is?

And if you've learned
You'll know much more than I

That you're gonna have to go and find it
You'll have to dig beneath the ground
You'll have to unearth every ugly stone
That kept you on your own
And simply put them down
You're gonna have to look around
-- Blues Traveller

The power to keep silent is many things.

Another way to state "Keep Silent" is "Contain," or "Internalize." Or "Ground." The ability to keep as one's own what one has brought about by Knowing, Willing, and Daring rather than watching it all evaporate in the first strong breeze.

The Power to Keep Silent is literally the ability to be silent. There is a time where that is appropriate. There is a time when it is tacticly prudent. There are even times when one's life can depend on it.

The power to Keep Silent is the ability to achieve a goal through subtle means rather than brute force.