Humans are not very good at estimating. We think a task will take 10 minutes and find that it’s taken us 40. This goes double for big projects that have many moving pieces. They also ways take longer than you think. The comic Isaiah and I are working on has taken about 10x longer than we expected. We’re committed to finishing it but we know that we’re going to have to change our process for the next project.
Estimating is hard, budgeting is easier. Instead of trying to figure out how long this project will take figure out how long you want it to last. Or even better what’s the maximum time you could bare. When you’re working on a personal project you have infinite time, as much as you need. The constraints are up to you. Figure out the time box that you want to put this project in. Is it a year, 6 months, 40 days. Then commit to that time and fit the project to the time box.