I think this is why it's super useful to have a cofounder for a side project: there's someone to let down (besides yourself) when you give up too soon. This is

I think this is why it's super useful to have a cofounder for a side project: there's someone to let down (besides yourself) when you give up too soon. This is also why funding (and employees) helps a lot of startups. Not so much the money itself, but an ever growing consortium of people who literally have a vested interest in the thing continuing. It's harder to give up when people are counting on you. If your side project isn't the kind where you want to make money in the end then you're going to need to have higher intrinsic motivation I suspect as none of these pressures will likely come to bear and help you stay motivated.