I have a pretty stressful job but I don't suffer from anxiety or any mental health issues. I do my best at work, in relationships (friendships, work relationships, etc.), and in life in general, and don't worry about things I cannot control. If something goes wrong, I just deal with it and try to prevent it in the future.
Realistically, what else could you do? Life is unpredictable and unfair. There are disappointments, and disappointments hurt. It's just life and life goes on, and we live.