The one merely requires will--and a great deal of it, both as to bulk and staying capacity--the other merely requires watchfulness--and for no long time.
The desire of course precedes the act, and should have one's first attention; it can do but little good to refuse the act over and over again, always leaving the desire unmolested, unconquered; the desire will continue to assert itself, and will be almost sure to win in the long run.

When the desire intrudes, it should be at once banished out of the mind.

One should be on the watch for it all the time--otherwise it will get in.

It must be taken in time and not allowed to get a lodgment.

A desire constantly repulsed for a fortnight should die, then.