“I don’t know how it could fail”
That’s a warning sign.
So is, “I don’t know how it would fail.”
In the first case, you haven’t thought deeply enough (or don’t have enough experience) to imagine how your solution might not work in every case. The best way to make your work better is to get more imaginative about how it could fail to resonate with those you seek to serve.
And in the second, once you can imagine that it might not work, it’s really helpful to imagine what failure actually entails. What breaks? What are the side effects? How will you recover?
The art of solving problems often involves spending time and energy on what you’ll do when you don’t actually solve the problem.