While it is true that Krishna may want to serve us by sublimating our sexual fluids for us, there are also simple techniques that we can do to facilitate this. I don't know if if's a Vaishnava aphorism, but my grandmother taught me that "God helps those who help themselves." Anyway, sublimating our sexual energy is important enough that we might want address it from a variety of angles.
Here's a few techniques to try:
First of all, be vigilent in the mind. Consider the progress toward action: thinking, feeling, and willing. Observe your thoughts, and catch sexual thoughts early in the process. If you are sensitive to your body, you may notice that the sexual fluids are drawn from throughout your body and gradually become more gross as your attachment to sexual pleasure goes from thinking to feeling to willing to doing. This decent fo the sexual fluid creates samskaras that act in a way that carves a path making it easier for the descent to occur in the near future. If you allow the sexual fluid to descend once, then it will be easier for the same thing to occur in the near future. Redirect your mind to spiritual subjects and create spiritual samskaras instead. Train yourself to remember Krishna whenever the idea of sex comes to mind, especially remembering His feet or the movements of His eyebrows.
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Also, there are exercises which are helpful. One that I've found to work well is described in a book called _Ancient Secret of the Fountain of Youth_ by Peter Kelder. It is mostly about a kriya commonly called "The Five Tibetans." Doing a search with that phrase will turn up a few sites that describe them. They're very good exercises to do. There is also a sixth exercise meant for those who are serious enough to be celibate. I haven't found it described anywhere on the Internet, but I'll try to describe it from memory:
1. Put your hands on your hips. Exhale completely.
2. Bend at the waste and place your hands on your knees. Exhale some more. Keep the breath out.
3. Straighten up. Keep the breath out. Place your hands on your hips.
4. Apply mula-bandha. (means: contract and raise the muscles of the anal sphincter and the muscles that stop the flow of urine.) Draw the diaphragm up into the rib cage. ("Uddiyana Bandha") Keep the breath exhaled completely. Keep your back straight. Drop the chin down, and then draw the chin back closer to the chest so the back of the neck does not round. ("Jhalandara Bandha") These three body locks combined form 'maha-bandha,' the great lock, sublimating and raising the semen.
5. Hold the complete step 4 as long as you can, with the breath out. When you must, inhale, then exhale again, beginning step 1 again. Repeat this whole procedure 3 times.
Mula-bhanda description:
http://yoga.about.com/od/howtospeakyoga/g/mulabandha.htm
Uddiyana Bandha description:
http://yoga.about.com/od/howtospeakyoga/g/uddiyanabandha.htm
Jhalandara Bandha:
http://yoga.about.com/od/howtospeakyoga/g/jhalandara.htm
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Sit in the pose that Hanuman is often shown. That would be, sitting on your left heel, with the heel between the anus and genitals. Right foot is flat on the floor with knee up. Hands are pressed flat together in front of the sternum. It will probably be uncomfortable at first, but it gets easier with practice. I learned this pose by the name "virasana," but I apparently don't know the correct spelling because I can't seem to find it on the Internet.
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Practice "Sat Kriya"
A description is found here:
http://www.susankezios.com/Kriyas/BASIC%20SPINAL%20ENERGIZER%20SERIES.htm
It's part 9 of this "basic spinal energy series." Actually, this whole set is helpful for what you're asking.
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Of course, if you set your mind on chanting Hare Krishna without deviation and without stopping, then your purpose is achieved. Personally, although I've been chanting Hare Krishna for almost 10 years, I haven't been able to chant it very nicely even once. These techniques I've described above are helpful too. Perhaps it's a part of Krishna carrying to you what you lack. Conquering the sex impulse is very difficult, but with practice it can be done, especially by attacking it on all levels. The kriyas described above hit it on the physical and mental levels, and remembering Krishna's name and form works on the spiritual level. Also, dancing in kirtan with the arms upraised is helpful for achieving this goal. Hare Krishna.
Your servant,
Pandu das