I think it's always best to apply. The worst that can happen is that you don't get accepted. If you don't apply you won't be going to school anyhow. If you do apply and do get accepted you don't have to go if you don't want to. On the other hand if you don't apply, and later wish you had, you lost a whole year.

Applying is kind of a pain, but basically all you need is your application, transcripts, letters of recommendation, and essay. Taking the GRE is the worst part, sign up now. The transcripts are easy to get because you are still on campus. Likewise with the letters of recommendation, but you have to check in politely with your professors to make sure they get sent by the deadline. The sooner you ask them the better.

If you don't go to school it's ok. Make sure though that you either get a job or an internship which will help you with your career goal (including applying for school next year). Do an unpaid internship or volunteer work if you have to. This is the time to do that sort of thing. I would think volunteering at a hospital, shelter, or that sort of thing would look good on a Psychology application.

You can also take classes next year part time. If you get good grades it could help immensely. Remember it's the fall classes (and summer if you do that) that count because you apply around Christmas. That's only one semester.

Starting now, you could ditch all of the classes that you don't like, or that are hard for you, and take only those that you really like or will do well at. Take only from professors that you like, and that like you. Only take as many classes as necessary. That way, even if it takes you another year to graduate your GPA will improve and your graduate applications will look better. Sometimes you have to take certain classes, but maximize your interest. It's really great to work on your weaknesses, and you should do that eventually, but there are times when it's best to focus on your strengths as well.