Just like we need to learn how to triage patients you need to learn how to triage your life. I'm half-way done with my 2 year nursing program and it can be busy and stressful, but I don't think it should ever be as bad as you describe it. If a test is worth 1/3 your grade you need to put much more time into that than things that are worth 1, 5, or 10% of your grade. Get a planner, write every due date out and start allotting your time to all your tests and projects. Writing papers is a skill you should hopefully have learned in high school or any other undergraduate liberal arts classes you have taken. Nursing papers are no different except you will use APA (a format that is easily copied from the internet). And to be honest, I don't think nursing professors are as strict with grammar and essay structure as the professors I have had with my previous degrees..
I didn't enjoy psych much either, but at the end of the day its a class and you have to learn it, so put the time in, it's really not that complex.
And echo those posts before, as important as schoolwork is, you need to add a few personal activities during your week may be regular exercise, dinner dates with friends or S.O's, as you like!