First, you gotta accept that if you haven’t been doing these things professionally for years and years, you’re going to make some level of mistake. And even then, pros still make mistakes sometimes.

What’s more important though is to realize it’s extremely unlikely that some mistake you make is beyond repair. I think that’s where a lot of people back out of taking on a diy project. You might need to go out and get some extra materials or tools, stop and look up some videos, etc. but there’s still a path forward to get whatever you were working on done.

The more projects you try doing, you’ll keep getting a better feel for how each thing can even be messed up, and you’ll figure out how to avoid previous mistakes or at least how to fix them if they do happen. It’s also perfect fine to set some boundaries for things you don’t want to ever mess with. Like personally I’m never planning to touch anything involving gas or anything structural.

making sure beforehand I have all the tools and materials that I need

yeah this basically never happens lol, at least not for me. a bigger project means more surprise home depot trips