I would agree with the other posters, going from nursing into teaching is very much frying pan to fire! Teachers have had incredible pressure added to their roles, with targets higher than ever. There's a reason these courses have been funded (of course, before the bursary was removed) - because at the end of your time at uni it's a lot of hard work and stress!
It sounds more like you're not cut out for shift work. Think about it this way, if you could do the job of a nurse in the times that worked for you, would you? If so, it's not so much nursing as a job that's the issue, it's lifestyle/working hours that are.
My advice? If you can stick it out, do so for a year, then see what other roles would be better suited. That way, you'll gain valuable experience and a brilliant start to your CV which will open more doors in the long run.
Like has been said, it's likely if you leave nursing before you've even started you might not get the chance to ever return. I wish you all the best!