I think it means "I almost wish I hadn't started."
Here's an example. Say you were carving a wooden figure wielding a sword. It turned out pretty good, but it didn't have the fingers yet. Since you wanted more details you started carving more to define its fingers. Turned out, it was more of a work than you thought it would be. 8 hours of carving and you still don't have fully defined fingers. Then you'd say either to yourself or your friend "I almost wish I hadn't bothered (carving the fingers for this figure)"
If anyone disagrees with my example or have more to add to it, feel free to express your opinions. HKB out.
Student or Learner