You can add meaning to your work by picking goals and accomplishing them. It doesn't matter what they are -- just as long as they can be accomplished and you know that you did.

Pick things that incidentally accomplish the assigned goal. For example,

1. Pick an amount of time, like 3 hours, repeat this cycle

2. make a branch

3. implement the feature in the fastest way you can

4. think about why this isn't acceptable

5. throw away the branch

6. do it again avoiding one thing that made the last one crappy

Also, weighing merits of different solutions and picking one is your job -- no need to feel bad about that. Come up with an assessment tool that will help you decide. Time-box decision making, but don't stop thinking about your solution -- just give it the appropriate amount of time, not unbounded.

Making progress is motivating. You want to end up at the same place but have the feeling of progress making throughout the process. I believe that it's possible you are taking the appropriate amount of time to do the work at hand, but you are getting into an anxiety/depression cycle because you can't get into a flow state.