Someone told me that he has a regret. Otherwise, his children might have a better life and he probably has a better post. Well....I think it is normal that we have regret in life. That is what makes us human.
However, my advice to him was.... just let go. We cannot bring our time back and rest assured that Allah knows what is best for him. His life is good at the moment and the only problem, he is comparing it with his friends.
Don't carry our regret as it does not do any good to our present life. Nothing ever happened in the past that can prevent us from being present now; and if the past cannot prevent us from being present now, what power does it have?