When faced with a continuing difficult situation, or perhaps you have tried something time and time again and not succeeded, what is the point of going on? Why don't we just give up and move on? Wouldn't that be much easier? Why should I put all this effort into something that may never work?
We would be in pretty bad shape if everyone had taken that view and just given up when things got hard. There would be no progress in the world. It is important to keep going despite setbacks and the inevitable self-doubt. The situation may change at the very next attempt, the next phone call, with the next meeting, or perhaps the next interview.
Sir Winston Churchill said it best, "If you are going through hell, keep going". Although the context in which this was said was quite different, the meaning is the same. Keep going, do persevere, hang in there, you just never know what is around the corner.