OK, here is one simple (although a bit wierd

) trick which I told other guys with similar problem and it worked great. (it also helps to extremly shy guys but it takes some menthal strenghts for right execution).
When you decide to aproach to some great looking girl, try to act like a guy who is in a LTR with the most beautifull girl in world. You "have" fantastic girlfriend waiting you at home and you are just having a night out, expecting and wanting nothing from other girls, only having a good time.
This will save you from big burden that you must seduce her, that you must not fail etc.. Afterall, you "have" a SHB girlfriend and if somebody happens with some other girl, good, if not, again good.
With that mindset you can be totally of pressure, funny, cocky, seductive, and being in that mindset does great stuff on field.