When the idea of any pleasure strikes your imagination, make a just computation between the duration of the pleasure and that of the repentance that is likely to follow it.

A pleasure arrives in the imagination at full size and with no receipt attached. What it does not show you is its own length, which is usually short, or the length of what follows, which is often much longer. The comparison is the whole of it: an hour of something against a week of undoing it. Most of what we regret would not survive that arithmetic done at the time.

When a strong pull arrives, do not argue with it. Just ask how long the good part lasts and how long the aftermath does, and let the two numbers sit next to each other before you decide.