I like and recommend the book Mini Habits and How to Be an Imperfectionist by Stephen Guise. He talks about the idea of setting goals small enough that you can't fail at them (like doing 1 push-up or writing 50 words) as a way to get started in improving your life. He contrasts this with the idea of setting bigger and more ambitious goals, which people struggle to succeed at and then give up on. I think this is an important idea.
Recently, I've had some success staying on an exercise routine by doing something I called self-negotiation. If my goal was to do 30 minutes of strength exercise, but I didn't really feel like it, I'd ask myself if 20 minutes of strength would do, or even 10 minutes. I've done similar with meditation, where my goal might be 20 minutes but I'd accept 5 minutes. This breaks down the goals into smaller and more achievable chunks, but I think the Mini Habits approach is better. Basically, I think my self-negotiation approach comes at things from the wrong direction. I'm still setting ambitious goals, with the risk of failure that entails, and then working backwards to something I can accomplish in any given circumstance. With the Mini Habits approach, you define victory in a very small, minimal way, and then everything after that is a bonus. I think that's a better way to approach things.
UPDATE: Note that I found out about Stephen Guise due to the Overthinking and Perfectionism post on the Critical Fallibilism website, so thanks to Elliot for that.