That's sucks, lab work sucks. I have a habit of putting things into my lab coat pockets, forgetting about them for 3 weeks, discover that they should have been kept in the fridge, and 9 times out of 10 they are absolutely fine. The moral of the story? odds are, it'll be fine. You're not the first person to make a mistake like this, and you won't be the last. It doesn't mean you're rubbish in the slightest.
The most difficult part of lab work isn't the intellectual challenge, the time managment challenge, or even the workload. It's the emotional side of things that is so very tough. Contending with failure day in day out, feeling like a fraud, cocking up, it all takes it's toll.
I'm know you'll figure out what to do to fix your problems. Whatever you do, don't be a coward and avoid going into the lab.