Focus on what you can do now

There were times when I kept doubting myself, and think that the reason there was no progress with the project is my incapability. I wasn't sure whether the problem is unsolvable with the current setup or I didn't work or try hard enough?

I asked that to one person I respected much. He said: list all the options I can do for this question, and do it one by one. When all items are done, check the status. Did it get solved? What are the takeaways? What can we do now?

Overall, try to accept that there will be something you ultimately can't do, but there is also so much you CAN DO and keep moving forward.