It can be difficult to do things that make you happy if you don't know what they are. Start compiling your own Happy List right now. List all the things, big or small, that create feelings of happiness for you, however fleeting those feelings are. Write down everything you can think of, then at the end of each day for the next few weeks reflect on your day and what made you happy, and continue adding to the list.
Make a point then of intentionally selecting something from the list and doing it; it can be at random times, once a day, once a week, or whenever you're feeling a little blue. Outside of the happiness created by doing something from your list, you're also creating feelings of self love and esteem by taking the time and intention to do something positive for yourself.
Need some help getting started? Here are some examples from my personal Happy List: