I get it sometimes but have tried and am trying a few of the tips mentioned earlier in this excellent thread.
Singing the first verse over the second is a brilliant idea. Haven't tried it.
Here's what I'll do to loosen up when the red light's on:
1 - I sometimes sing without headphones, depending on the song it sometimes work and sometimes not.
2 - Very often I do what Paul does, remove my left (it's always the left for some reason) headphone but keep the right one on. This usually works.
3 - I practice singing the song (I tell myself) while having the red light on, I'm stupid like that and very often it's one of these takes that makes it.
4 - I try as often as I can to sit and noodle and sing with the headphones and red light on just to get used to it.
5 - If none of these things work, right before I start recording, I listen to a couple of songs I like, like really listen, to songs that sound a bit like the one I'm working on. I listen to how they sing, how they articulate and what feeling they try to convey and I then try to get into that mood and copy that feeling. Shortly thereafter I record. It usually works wonders.
Cheers,
S
Edit: Oh I almost forgot, what I've stopped doing is to record a demo take. You know when the lyrics are only half finished or sometimes there aren't even an existing lyrics. I've stopped doing that completely. That only leads to a demo recording you will fall in love with and in the end is absolutely impossible to match and it only increases the pressure when you're ready to record the actual vocals. No demos, record only what you're ready to keep is my final advice.