I think its usually when the project becomes a burden (the author notes as such in the conclusion), this is a bit simplistic as sometimes you just have to push

I think its usually when the project becomes a burden (the author notes as such in the conclusion), this is a bit simplistic as sometimes you just have to push past this to get somewhere, but if its a hobby project it should bring you some joy. When you see yourself doing fake productivity its bad news. I also find that sometimes I will scope tasks too big, take too long to finish them and get demotivated, if I break them up further I can keep momentum (even if the breakup is during the original task). Having said that I don't think giving up is necessarily a failure case that people think it is, I often take a lot of learnings after attempting to do very ambitious projects that I eventually scrap, but the learnings stay with me.