Full disclosure: I am not particularly intentional about "mindfulness," and finding the tools that work for you individually is key. (For example, my meditation is going on walks.) But related directly to work productivity, I'll share my personal experience here:
I've found shipping faster and iterating quickly (i.e. delivering something, even — maybe even especially — before I felt ready) has made me way more resilient. It's not just big things like product releases; it's even small things like sending an email to someone important or booking a flight. In doing so, I learned that most "failures" are survivable and that even the worst-case scenario is never as bad as I had feared. This practice basically killed anxiety for me.
As an entrepreneur, you have incomplete information. But you always make the right decision because you make it the right decision. You adapt after the fact. It's an exhausting and often psychotic rollercoaster, but it's just the nature of the profession.
When I am overwhelmed with analysis paralysis or with plain ol' anxiety, I find that focusing on one, achievable thing helps me pull myself out of it. For me, in a way, anxiety is the inability to get. over. yourself. and to just be open to imperfection. Setting expectations is key here (for example, setting the expectation that this is all an experiment, and we're humans who fuck up), and being good at managing expectations is the best possible thing you can do for your business and your personal well-being.
Obviously, don't Hail Mary everything you do, but shipping early and often really did make me more comfortable with pushing things forward, regardless of how imperfect they were at first. Then, I learned what things to prioritize and what things I could afford to slack on a bit. And then I realized that half the things I was stressed about are not worth the brain power!
But also, just finding other founder friends to talk you off your weekly cliff.
Hope this helps!