Here are three techniques you can use to keep yourself under control when you feel you're overwhelmed by a woman's beauty.
1) Pick Out A Flaw
The first technique you can use is to pick out a flaw on a woman's face or body when you talk to her. For example, if her nose has a funny shape, then try to "find that funny" and think about it as you chat with her.
2) Use The Old Boxers Technique
The second technique you can use is to imagine the woman in a pair of old, funky looking underwear. This technique is actually used by actors to overcome their stage fright when they audition for roles in movies. I have no idea why it works for many people - it just does. See if it works for you too.
3) Hang Around Beautiful Women More Often
The last technique is a long-term technique. You should try to befriend beautiful women and just hang around them until you're comfortable hanging around or having frequent physical contact with women. Don't worry about hitting on them or getting into their pants. You're just using them to train yourself. In time, you will be "used" to having beautiful women around you and when you meet a new woman who's considered beautiful by most guys, you won't be scared to approach her anymore.