In your case, take some money out and get some coke and a hooker.
Keep bouncing back and forth until you feel comfortable at the 50NL tables. The only issue is in your head. I have had similar issues in the past. And stick to the 20 buyins for each NL level. If you are having troubling with feeling comfortable at a higher level even though you have the bankroll for it, it suggests that you would be playing wicked scared if you strayed into the 10-15 buyin range.
After the coke and hooker, I think you will be more relaxed at the higher levels.