Many ways, but why? It should be harmless as long as one does not use too much force or friction on his or her genitals. Realize that the body has essentially the same response to masturbation as to sex for the purpose of reproduction. That means the body reacts just as it does during sexual intercourse, which of course, has no harmful side effects on the body. If the habit is causing anxiety, there are ways to stop.
Where? When? How? So is there something inappropriate about how you do it or what you do, as in fixated on a person, object or something taboo? If so we can only say it is time to see a professional therapist. If not, then read what my esteemed colleague rk wrote.