One thing that helped was stopping to think about why I wanted to do each thing.

Boom. This was big for me too. Usually my issue is holding myself to non-existent time constraints, like "I want to do X but I have to get Y done or I can't until next weekend." Ok, why is it a problem that Y can't be done next weekend? Obviously if it's something like a chore or errand it doesn't apply, but if it's just a little side project I've been working on, Y can wait if I'd rather do X, especially if I'm just going to sit and wallow over not doing either instead.