There are so many great answers here of things to do to address singular areas. But my top life hacks have to do with understanding fundamentally how to improve the self (and thereby take advantage of the wonderful answers here.) To me, life hacking is how to hack my life (for happiness in my case), not how to hack the things in my life.
1. The mind is recursively aware and you can use that to your advantage. When you think something, you can continually assess why you thought what you thought. This allows you to separate your functioning mind from your thinking mind. This is why we can improve ourselves with simple rules.
2. The mind is a junkie that craves dopamine and serotonin. Knowing this and #1, you can rewire your brain to respond to completely different stimulus and effectively change your entire behavior and outlook. Some of us may need medications to stabilize our minds long enough to engage in such practices and may never respond to medications enough to engage in such a practice, but the underlying principle is still true. Afraid of something? Try having sex right after you encounter that fear. The next time you see your fear, you will be slightly sexually aroused and that can help push back the fear hormones and give you a better functioning brain as a result. Just one example.
3. Fear is a useful guidepost but a terrible master. If you feel fear, you are addressing something that is basic to who you are. You can use fear to reliably point you to areas of your mind that require attention. Just as children have boogeymen and real fears, so our mind has built up notions that scare us away from the truly important part of ourselves, sometimes those parts that while painful are comfortable because they are known and we have coping mechanisms for. Where there is fear, there may be good reason to be afraid, but you won’t know it until you face the fear. In conjunction with #2, you can overcome your fears by redefining the dopamine you receive from the fear.
4. You’re an animal with basic animal instincts of survival. This means that we have many shortcuts in our brains to help us avoid thinking and simply act in response to stimulus. Use that to change yourself, too. For instance, yellow and red are signs of danger. It’s not always true, but as a general rule, it’s pretty helpful. Being aware of what is making you feel the way you do and trying to understand whether the reaction is instinctual or learned will help you a) realize when you’re being manipulated or b) being led astray by your own instincts.
5. We live the lives we are most comfortable with – regardless of how painful we might perceive our lives to be. Think about that for a second. Is there something in your life that you hate? The question is not how do I get rid of this thing I hate, but rather why do I keep putting up with this thing? Why do I keep going back to it and obsessing over it? If you cannot answer it, let it go because it’s not the real problem. That means you have to live with yourself in odd ways for a while until you are ready or aware enough to deal with that thing. This frees you up to focus on the things that you can immediately change and which are truly problematic for you. Do you think you’re fat and that upsets you and yet you remain fat? Perhaps you have a medical condition or perhaps you’re happy enough in your life that being fat doesn’t really mean anything. Or perhaps being fat is a protection mechanism in some way and it makes you feel more comfortable to be fat than not to. Either way, if you’re not really changing it, you don’t really want to change it. That doesn’t mean you’re bad or wrong or any other negative judgement. Sometimes our unhappiness comes from the theft by expectation put upon us by a society we didn’t construct for ourselves. This is the essence of Emerson’s quote, “The majority of men lives in quiet desperation.”
6. Meditate. Often and vigorously until you die. I don’t do it enough because I let myself get distracted with other things too often. It’s also not a cure all for what ails you. BUT it is the single best exercise you can give your mind and has the most payoff for a happy and productive life (productive by human standards not capitalistic standards ;) ) Even if you think you can never calm your mind enough to meditate, just spending 10 minutes a day with everything turned off staring outside can be enough to bring a deep sense of calm to your life.
7. Accept that just like you, everyone else is living their life as best they know how – even if you know a better way. This is the root of compassion and forgiveness. Try not to look at people doing stupid things and say to yourself, “Oh, my God, they know better than to do that.” or “What the hell were they thinking?” Just let go of that thinking and say to yourself, “They’re doing their best and maybe one day they’ll be better than me but they are learning and I am not their teacher.” Accept without judging and you will be happier and that happiness will be returned to you in the way you deal with others.
8. Accept the apology you’re given not the apology you wanted. You may not like the apology you’re given, it may not address the points you wanted it to, it may not be in the language you wanted it to be in. It may be a somewhat selfish apology, or an ignorant one. It may not even be sincere. That’s not your problem to deal with. Apologizing is a form of growth and when we take the time to apologize and consider others, we expand ourselves to cover the consequences of our actions. If we don’t sincerely apologize, then the failure is within ourselves not necessarily a failure to others. This doesn’t mean you have to take every apology and forget whatever transgression the apology attempts to address. You can and should still remove people from your life who don’t live a life in accordance with your physical and psychological well-being. And of course, if you can, keeping #7 in mind, try to help the other person understand what you need from them (not what failure they created in their apology) and listen to what they are trying to tell you they intended. Ideas are great, execution is flawed and that goes for apologies, too.
10. Life is short, waste more of it. This is one of the great paradoxes of life. We are not machines who are happy wrenching every second of every hour out in some kind of pursuit. We enjoy life more when we experience life, not exist to live life at some point in the future. So many people – too many people – think things like “When I get this promotion, we’ll do more together”, “When I get older, I’m going to X” It’s good to have plans and look forward. Don’t get me wrong. Someone else here mentioned something I agree with that for every one thing you bring in to your house, you should take two things out. I agree with that for your life, too. For every future thing you say, say two things about now. If you have a bucket list, with ten items, pick 20 things you like about now, or the current people you know. It can give you a lot of perspective on the trap of “efficient time use” that isn’t efficient for our happiness, only our production. Don’t feel guilty for wasting a day, dont’ feel proud of it, either.
I skipped 9 because I don’t like being forced to say more than I have to offer. I’m not a machine. ;)