Year 13 A2 student here doing English Lit, Psychology, Spanish and Art. Don't get too frustrated and stressed if things aren't going as you hope - the best thing to do is keep organised and if you're not organised, get organised! You will feel much better as a result. With A Levels, you either do very well or very badly. I'd suggest making sure you thoroughly go through your content and revise over it frequently. Also, try to actually enjoy your subjects as you'll do much better if you have a motivation for doing well.
Good luck with A Levels!