Dear Dr. Kolbe, What a great read.  Thanks for making it available. I first encountered this topic in my twenties with Mantak Chia’s book. But semen retention was a difficult task back then! Now in my fifties and facing down a very difficult cancer, this process has become much more relevant.  For sure now I have to carefully manage my energy, and I know that if I release it, I’m down for days, and if I preserve it and pull it back into my body I feel energized and healed.  I would bet I’m still alive partly due to this. Very important in your book you point out that sexuality is as important as diet and exercise.  I will take that to heart and be more serious with my practices!  Also, I think your book is unique in promoting solo practice.  All the other literature seems to imply you are unclean if you don’t do this with a partner, which I think would be impractical.  Surely the monks throughout the world and throughout the centuries have masturbated their way to enlightenment.