I often think of this geeky comic when the subject comes up: http://existentialcomics.com/comic/13
e.g. $10 is most useful right now, slightly less useful a day from now, and much less useful a year from now. This is for real reasons -- inflation -- and psychological reasons -- I'm more excited about getting that $10 now than in a year.
There are equations for this stuff but it's been a long time since college.
You can replace $10 with other "goods" like time, sleep, relaxation, etc.
That phrasing helps immensely. Sometimes it's worth it to push out the pain, but usually it isn't.
I often will consider my past and future as a separate entity or person than myself today in the present. And acknowledge things theyve done good or bad. Or to be kind to your future self as if you are doing a favor for a close friend.
This might sound weird but I try this sometimes. "Thanks, past self, for having done this on time, now I can enjoy the weekend because I'm done with this tedious work!" You don't have to literally talk to yourself or anything, but it's IMO a healthy state of mind. It's also the only way I've found to directly tackle the underlying problem of procrastination instead of just telling yourself to "not be lazy, stupid!".