I ab-so-lu-te-ly agree with what your therapist told you. Mutual masturbation is something we did in the beginning as well, but as you wrote, after a few months or years there were occasions on which my husband was in the mood and I wasn’t and I asked him to wait until the next day. By that time, he already solved the problem by himself. 🙂 So he gradually started doing it more and more on his own, and asked me less and less to help him out. Exit the last sexual intimacy that was left between us.
So when I started my therapy, I was given a brochure and one of the tips inside was to stop masturbating COMPLETELY and basically force your partner to tell him he was in the mood. Either I could help him out, or when I really didn’t feel up to that, he started masturbating in my presence. Sometimes I just let him do his thing, sometimes I “helped” him with kisses, cuddles, and I even sometimes got turned on anyway and took over from him.
Similarly to what you wrote, our communication on sex is now even better than before. My husband didn’t masturbate in private for over 10 months now, but we feel closer than ever.