How to cultivate positive emotion?

Hi team. How can I feel better? I assume the answer would be to change my thoughts. But sometimes, I get into slumps and I find it difficult to get out of them other than just to get a lot of sleep and do some exercise on the weekend, which tends to “reset” the way I feel and I’m calmer and resilient.

I’m thinking our thoughts are like our bodies in that we need to practice exercises to be fit and healthy, so we need to practice positive thoughts for our brains to be fit and healthy.

If that idea is sound, then how do we practice helpful/positive thoughts, and how do we know we’re on track? What’s the evidence to show, yes – the “thought workouts” that you’re doing are positively changing your brain?

I want to feel better and live my life fully, but I am tripping myself up somewhere (even just writing that I see that I think I need to feel better in order to live my life fully!)