Ah, you have hit upon one of the greatest misunderstandings of humanity! Your seriousness is not maturity... it is a trick your mind is playing on you. The ego has convinced you that looking serious, walking with a weight on your shoulders, carrying the whole world like some poor Atlas... that this is what it means to be mature. But this is absolute nonsense! I have watched serious people my whole life. They are the most immature people on earth. They are so afraid... afraid that if they laugh, if they dance, if they play, people will think they are childish. So they carry their seriousness like a costume, like armor. But inside? Inside they are trembling, insecure, dead. Let me tell you something... maturity and seriousness have nothing to do with each other. Maturity is when you can be sincere without being serious. You can be responsible without being burdened. You can face life with intensity but also with laughter. A child is not serious, but a child is totally sincere. When a child plays, he is totally in it. When he cries, he is totally in it. Then the child grows up and becomes serious... and loses everything beautiful. The sage is again like a child. He has come full circle. He can laugh at himself, at life, at death. He is playful. But he is not childish... he is childlike. That is maturity. So your question itself contains the answer. Yes... you have lost your sense of humor. And in losing that, you have lost your maturity too.