Not so much “life-hacks” but things that have made me successful(ish):
Exercise really is the solution to so many of life’s issues (moods, health, etc.).  It’s not just hype.  My entire life has been changed in monumental ways because of exercise.  If you’re not getting enough exercise (or unless you are one of the rare like 1% of people who genuinely can be healthy without it) then you are suffering in some way.  It doesn’t have to be CrossFit or running marathons, but you should be exercising.
Make a list of your priorities (including people).  Update it as necessary, but refer to it frequently.  It will help you make decisions on what is important in life.  It’s cold.  It’s calculating.  But so are you, we all are; we all have priorities (and we hate to admit that we rank people and things, but you do, we all do — I’m just honest about it and write it down; if you’re in my life, you’re on the list).  The difference between those who cannot prioritize and those that do is about two heartbeats in making decisions that most people agonize over.
It’s better to do things than to have things.  I’m not rich, but I can do one or the other.  I can afford nice things. I could have all sorts of great shit that people would look at and desire.  I can travel and do things and have great experiences with my husband.  But I can’t do both.  Doing things together builds your relationships; having things seems to distract away from what’s important.

Okay, and one more:
If you have plans, have re-evaluation periods and benchmarks.  It’s hard.  It ain’t fun.  But if you don’t have goals and dates that those goals need to meet, then you are unlikely to succeed in a lot of things you try to do.  Your goals should be flexible (mine change all the time), but the ones I have, have evaluation periods that I look back and think, “Why am I doing this?”  If I’m not on track to meet the goals, if I feel like I’m missing the mark (or that it’s no longer worth it), I evaluate and change course.