How to be happy🤔

I hit rock bottom the other day and I realized I haven't been genuinely happy in a long time. Ever since December of last year, I've been having it pretty rough because my life's been a roller coaster of "This isn't so bad" and "Damn, this sucks." with the very rare "Things are great.". I feel like if I started to be genuinely happy and find my own happiness within myself then my life wouldn't be as hard and maybe things would turn around. Where and how do I start?