This might be easy for me to say: I’m quite blessed and I have so much good stuff going on. However, I still believe that it is a conscious choice to be positive. To look at the bright side of things. This is a way of thinking you can force yourself into.
It is important to make the distinction between happiness and positivity. Being happy can be really hard or just impossible when you just went through something horrible. But in every situation you have the choice to focus on the things that actually are good.
You have the power to dismiss negative thoughts and focus on the positive things.