List three new things you are grateful for. Not just the what, but the why. This encourages your brain to find the good in your life. You’re rewiring yourself.
Write. Every day, take 15 minutes to write whatever happened to you the day before that was most meaningful. Your brain experiences the most meaningful instance of the day before twice: once when you live it, once when you write it. You create a trajectory of meaning through your life.
15 minutes of fun, active, cardiovascular activity every day. Exercise is powerful and known to incite other positive changes.
Meditation. For two minutes a day, do nothing but watch your breath go in, and go out.
If you achieve happiness with others your happiness reaches "full potential". Our happiness is connected to that of people around us. So, connect. Every day, take 3 minutes to write a positive email or text praising a person in your life.