They said in high school, "your'e normal if you do, your'e normal if if don't". Lets face it its a normal and healthy adult activity that the majority of us do. There are so many health benefits in self pleasure for both men and women!
Men: The benefits include increased dopamine in the brain after orgasm, although this may make you tired its actually good for you, it is proven to help with depression, and to reduce the effects of anxiety. Regularly ejaculating also highly decreases the chance of prostate cancer. So it's a no brainer, go for it.
Women: The benefits also include increased dopamine in the brain, it makes you feel good. It is also good for you, lifting your mood and also helping with depression and anxiety. Regular masturbation will also help with preventing cervical and ovarian cancers.
It seems the answer is simple, its healthy, its fun and it works!
Couples: Mutual masturbation can come in many forms. Why not bring toys into the equation? There are many designed for couples but female toys can also be great for males. Hot tip guys "Try your partners wand, you won't regret it". Watching each other play with toys can be a huge turn on, see it as foreplay.