Don't try so hard... no pun intended.
You're mind fuc*ing yourself. You're getting all excited and anticipating the event that's about to happen and hoping you'll be able to do what needs to be done... and you're focused on "the act".

I say... just chill. Step back, slow down and cool off.

There's nothing like just holding and cuddling and touching in a non-sexual way. Perhaps you can give her a whole body massage and let her give you one. Get familiar with her body and let her get familiar with yours. Take a short nap with her if the two of you feel like it. There's nothing like a good massage to relax you enough for a quick snooze. Stop thinking about what you've got between your legs... and certainly stop thinking about her equipment. There's plenty of time for that...

Touch... play... caress... focus on giving her pleasure... keep it relaxed, humorous and light. If you're concerned about performing, or more accurately, NOT performing, just remember, there is a whole universe of ways to please a woman without having sexual intercourse with her. If you aren't sure about what she might want, or what to do, just ask her. I'm sure she'd be happy to teach you "the fine art of pleasing a woman". You said she wanted to teach you. Well, there ya go.

Take plenty of time for long and sensual foreplay... do everything slowly and gently... there is no rush. When you're both ready to do the deed, you'll know whether you're ready or not. You should be calm yet aroused, mindful of what you're doing and relaxed about it. Make putting on the condom a game with her participating... and not something you've got to quickly put on so you can put it to good use. Nope. Slow and easy with no rush and no pressure. Trust me, there is a time for fast and rough and heated, but this isn't that time.

In MY world, something like this whole glorious event shouldn't take anything less than two hours... minimum.

Anyway, I probably said WAY too much here, so that's all I gotz to say 'bout that!

Dan