Regret for wasted time should be deep, for time passes quickly and it is difficult to make up what you have missed.
Time for the worshiper is a time for worship and reciting awraad, and for the devoted Muslim it is time for turning to Allah and focusing on Him with all his heart.
Time is the dearest thing to him and he would feel very sad if time passes without him doing what he is meant to do. If he misses time, he can never make it up, because a second time has its own duties. So if he misses time, there is no way he can bring it back.