I got over both the starting paralysis (and then the subsequent doubt paralysis that I picked the wrong one to work on) by doing 2 major things:
1. Making the definition of "project success" being that I learned a ton.
Once I did this (like consciously did it, for example my decision to work on E2EE was a terrible biz decision because nobody asked for it, but I wanted to learn more about cryptography) the decision became easier. I picked the one that had something I wanted to learn in the immediate term. Mogul had more interesting things at the time that I wanted to learn (E2EE, push notifications, CSV uploading, etc...)
2. Choosing to work on these projects over a very long period of time. Once I had the mindset that these were 10+ year projects for me, the approach really stopped mattering to me. As long as I pushed forward, I felt like I was going in the right direction.
Working on 1 feature per app each week vs focusing 1 year on each app stopped mattering because the end result over a 10+ year period would be the same. Both apps would be there, probably have similar features and I would have learned the same things. Just in a different order.
Second one is definitely more specific to me, but I think some of it can be applied when you think about a project/product as a small part of someone's life journey.
Hope that helps!
(edit: I also wanted to say that I have 2 more apps on my roadmap. No idea when I'll start them but I know the I'll do it when the time is right)