Depends on the purpose of your side projects.
Is the main aim to explore things that interest you or is it to "ship" something specific?
If it is the former then perhaps you shouldn't worry and just let the rabbit hole lead you where it may.
If it is the latter then perhaps it would help to produce some sort of roadmap. Ideally share this and get other people involved (either people who will work with you on it or who want to use the finished product) and they will perhaps keep you somewhat accountable.
If your side project involves multiple difficult problems then perhaps you need to accept that it is not going to be a 1 person job to get it done too the quality standard that you aspire too.
Comments
Depends on the purpose of your side projects. Is the main aim to explore things that interest you or is it to "ship" something specific?
If it is the former then perhaps you shouldn't worry and just let the rabbit hole lead you where it may.
If it is the latter then perhaps it would help to produce some sort of roadmap. Ideally share this and get other people involved (either people who will work with you on it or who want to use the finished product) and they will perhaps keep you somewhat accountable.
If your side project involves multiple difficult problems then perhaps you need to accept that it is not going to be a 1 person job to get it done too the quality standard that you aspire too.