There seems to be a general trick to expecting more of yourself.

I can get more willpower by thinking "I don't have enough strength, but I put myself in the hands of the Lord, who'll give me his strength" - and I discovered that trick long after I became an atheist! I suspect the trick is to enforce the expectation of undepleting willpower, which makes it true.

It might be a rigged self-test. Where else can we test if the trick works?