All excellent responses I will add a bit from a differing perspective however..
I would be careful not to beat myself up over this thing. At certain ages it could be called completely natural. Not preferable and a cause for loss of focus and some other negative things but a thing which most all at certain ages engage in some form.
If one is like me perhaps you may try to engage this thing with a quiet mind if one has that training.
You will perhaps find it quite impossible as I have. The thing may still present after doing this.... but with changed character and a lessening of objectification. So if you are like me you don't transform it or anything like that but it just changes its character by itself if engaged in this manner. So if I wanted to change that and have not the training I would engage that training.
I of course am only a uneducated layperson with no accomplishment. But to me it seems that sex is as some say...... related to a quality of awareness that emphesizes the differentiation of objects. What is different as opposed to same, as aware function. So if not present in sexual form I think objects, sunlight trees whatever, have a resultant effect of brightness quality and depth. Perhaps the visual being the most sense related to ascertaining discrimination(just guessing).
So I'm guessing that when not engaged, the resultant effect over time.... is everything seems very bright. In a coloquial sense that may allow for the folk tale that doing such things make you go blind
It seems when not engaged for any reason over time... things do seem brighter as effect. Of course one however does not go blind....that is silly.
And at certain ages I'd say for a nonmonk it is practically impossible to not engage this thing in some form. Setting up a dichotomy of wrong or right, good or bad, this thing or the spiritual I would say would be unhealthful, as it sets up a habitual response of a exclusionary sort. I do not this thing I am spiritual.
I fight this thing and become pure... Just me again but I would never try to exclude as spiritual path.
That is my personal opinion for one who is as I am. Others may certainly find better personal approaches for their type. Some may exclude with great success...I don't know just know I can not do that.
In the school I have practiced in...one meditates with eyes wide open, straight ahead.
REally after all we are human. SEx is not all that important at all, but obsessing it can make it seem way way important. A monk carrying a woman on his back over a rageing stream, dropped the woman on the other side and walked on. His companion carried the woman in his mind until darkness when camping he asked the first monk if what he did was proper, carrying the woman. He responded of course....he had dropped the woman at the stream bank and you have carried her these many hours.
So that means...don't make a big deal over it nor pretend one has circumstances in which such circumstances never present. They do..but not a big deal.
To add to the other excellent comments..pick what you like.
"This order considers that progress can be achieved more rapidly during a single month of self-transformation through terrifying conditions in rough terrain and in "the abode of harmful forces" than through meditating for a period of three years in towns and monasteries"....Takpo Tashi Namgyal.