If only I would have done this or done that, then I would be happy. Thoughts like these are hurtful and get you nowhere. The past is the past; it can not be changed. Focus on what you can do now to achieve your goals. Keep working forward and not backward.
We all need to realize the more we work together, the more we can achieve. We need to start building each other up instead of putting each other down.
Understand you will make mistakes and you will fall down. This is part of life. But know that you must get up and learn from the mistakes. That is how you will ultimately succeed.