One of the biggest stumbling blocks for many of my projects is indecision.
As much as the old timers complain about software and fast micros ruining things - we really do live in the best times for hobby electornics, with a huge range of very cheap parts and prebuilt modules available almost everywhere.
The only downside of such an abundance of solutions is - theres no real restriction on the number of ways to achieve something, so instead of being forced to use, say, TTL logic or a cheap opamp for a solution we now have to choose between many possible designs, all of which are pretty cheap and easily avaiable. So there often isn't any need to be "clever" with what you have, its just quicker, and easier to throw an Arduino or Pi at something. Sure you can design it differently for the sake of being different, but often that requires more time, which is great for a hobby, but if you're sharing the project so others can build, it'll just be another hurdle for them.
When I first replied to this thread I checked my notes to see how many projects were started but incomplete, that is,
on-going - anywhere from
already bought the parts for it to
half finished prototype board or
written a library, but not a main code and it's easily over 30