If you're a psychotherapist or a psychiatrist, you deal with lots of patients who have a variety of issues every day. And some patients will be doing better than others.
One patient you'll see will be doing well and will be making lots of progress in overcoming his or her mental health issues. Then the next client you see a little bit later on in the day will be doing just awful and will be having a rather bad day. Or vice-versa.
Also, some patients get better with the help of psychiatric treatment quicker than others. And some make much more progress in the long term than other patients you see.
So if you're a shrink or want to become one someday, you'll really be dealing with a variety of emotions each day you see your patients. You have to be ready for it as well.