Truly there is a tide in the affairs of men; but there is no gulf-stream setting forever in one direction.

Favourable conditions are real, and they are also temporary. A run of luck, a rising market, a period when everything you touch works: these are genuine and worth using hard, but nothing runs in one direction forever, and the people who forget it get caught holding the assumption. The same applies when things are against you, which is the more encouraging half.

If the current is with you now, bank something for the turn rather than spending as though this is the new baseline. If it is against you, hold on and keep the machinery in good order, because conditions do change.