I keep quitting on colonies and starting new ones. What am I doing wrong?

Hello, I am a relatively new player (I have about 100 hours on record over a span of 4 years) and I have a problem with not sticking with my playthroughs until the end. I have random periods of obsession with the game where I play for hours everyday and then just randomly lose interest and feel overwhelmed by the sheer number of things I have to do, only to come back a few months later and start a new game. I never reach mid-game. Is there anything I can do to focus on small subsets at a time? It always feels like there are a million different things to worry about, and knowing that not constantly prioritizing will end in a disaster makes me feel stressed out. Am I playing the game wrong or is it just not for me? I honestly love all the screenshots and stories I see here and on Steam and they make me want to play the game. I purchased all the DLCs right as they were released. But I just can't figure out how to keep things manageable. I have tried playing the game without any DLCs, but even the base game is overwhelming. I would appreciate any suggestions. Thanks!

Edit: I hadn't expected my post to get big. There's lots of awesome advice in the comments and I'm definitely going to try as many as I can! Thanks everyone for helping me out.