There are moments when we all have doubts when it comes to our own lives, but what we need to remember, is we are in charge of how each of our own lives works and runs, and no one else. No one should have the power to control you or tell you what is right for you. They can help, but not take over, because in the end, it is all down to you!
You may not believe it yet, but you can and will win. Just believe in yourself. It is there, the strength you are looking for, is there.