[awlo]

Isn't that an 'egg and chicken' type of problem? You can, after all, learn self-control / to defer gratification.

[quantumhobbit]

chicken and egg indeed. It's easier once you have better self-control to learn better self-control.

I've discovered that practicing meditation helps me a lot with self-control.

[joe_the_user]

It is situational.

You practice self control in situations where you have a reserve of self-control - say, in your own house before bed time. Theoretically this will let you build up a greater reserve for situations where you need more self-control - confronting a subordinate or superior on a job.