Masturbation is not mentally/physically harmful no matter how often you practice it. It's a personal and private thing so you may not hear people talk about it but most people probably do it at some point in their lives. Some cultures think masturbation is a natural part of boys and girls sexual development. Others consider it shameful. The decision is yours. If you want to do it less you could try to slowly reduce the number of times you do it daily/weekly.
Attribution: Straight Talk Foundation