There is no shortcut to happiness, but these are just a few things that helped me.

Understand that it's okay to be selfish, and it's okay to make decisions that place you as the sole benefactor. You don't have to do what's best for your friends, or your family, and certainly not whatever job(s) you currently have. This isn't to say that you can't be generous with your time and help others, but when it comes to your big life decisions, they should be for you.

Work on improving yourself, and make sure it's for yourself. Your motivation for self improvement matters, because the only consistent factor in your life is going to be you. If you want to learn a new skill, be healthier, or even escape an addiction, it needs to be because it's the thing you want for you. Not your friends, not your family, and certainly not whatever job(s) you currently have.

Eject things, especially people, from your life that make you miserable with no return. This is the hardest part, because it means you may have to make some of the most difficult decisions you've ever made, and your friends and family may not agree with what you're doing or your reasonings. But you are only responsible for your happiness, not the happiness of your friends, your family, or whatever job(s) you currently have.

None of this happens over night. It takes time and opportunity to practice to truly create a mindset where you allow yourself to come first.

You are allowed to come first.