Two things jumped out at me when I read your post. You are showing signs of depression or burnout and you put one single word in bold.
Do you have a preceptor or clinical instructor that you trust? Is it possible to explain to him or her what you are experiencing and ask for suggestions about coping strategies?
Personally I find that exercise is a great stress reliever. If I've had a bad shift I usually go to the gym or go for a run. I don't know if that'll work for you?
If a negative image from work pops up in my mind during my off time I usually acknowledge it. Yes, this patients plight pains me and I feel for them. Then I firmly set the thought aside and replace it with another more positive one. You say that you love the moments when you helped a patient. Held their hands and smiled at them, and have them smile back at you. Focus on that! Make that the image in your head. You already had plenty of moments and will have many more in the future where you make a difference in a persons life. Use those moments for mental sustenance. You won't be able to fix everything that's wrong and unfair in the world but believe me, your professional knowledge and your caring attitude will make a difference in a lot of patients lives.
I knew early on during school that the typical med-surg floor or any kind of long-term care was not for me. I dread it for so many reasons. One of them is that I don't want to form long relationships with my patients. If I do, they will inevitably (for me at least) spill over in my private time in a way that I don't find beneficial. I found my happiness to some extent in the emergency department but even more so in the pacu and snooze
side of an operating room. I love the chance of for a couple of hours focusing on one patient at the time (well, two in the pacu) and making a huge difference in their lives. Also I have a huge interest and fascination with physiology and pharmacology and my chosen path stimulate/challenge me in those areas.
I think that's the charm of the nursing profession. There are so many different type of jobs within the profession that I believe that there is a match for almost every type of personality. Perhaps some of the angst your experiencing right know will resolve when you gain experience in your new profession. Nursing is a high-stress job that often demands a lot from you. I think that you need to find the niche that offers you fulfillment instead of anxiety.
Best wishes to you OP!