Aside from infectious diseases and surgical illness, it's somewhat scary to realize that there are no cures to things. We can't cure crap (literally and figuratively). All the big deals - cancer, heart disease, stroke, HIV, high blood pressure, diabetes - we can't do anything for other than try to prevent or try to make the disease tolerable. We are impotent.
It took me a while to realize that most of what I do is delay the inevitable. We all die, no matter what, and the only thing I have to offer is delaying premature death. Otherwise, if you're 83 and dying of metastatic colon cancer, then that's about right. And it took me even longer to see the value in doing this Sisyphean work, an endless stream of hypertensives and poorly controlled diabetics.
So if you're going into medicine to cure people, then please reconsider.