Yes, you need to stay on top of your mental processes. You can think about sex, but the more you do so, the more strongly you'll build up charges in the astral light, and those will not only attract more such feelings and images to you -- they can work down into the material plane and put you into situations where you can express those thoughts and fantasies in the material world.
One exercise you may find useful to redirect your energies is in this book:
Re: Desires reflected in the astral light
Date: 2023-08-07 07:13 pm (UTC)One exercise you may find useful to redirect your energies is in this book:
https://archive.org/details/rosicrucianmanua00plum
You'll find the exercise on pages 44-45. This works best if you have an active spiritual life of some kind.