Sjdent:
You're not the only one so don't feel that you are. You would have to explain your situation more thoroughly for us to give you a better feedback.
For myself, there were definitely moments where I get discouraged either because of a grade I earned that was below my goal or get stressed when I have exams after exams to study for.
In addition, being a class officer there are definitely more stress and frustration than being a regular classmate because I have to deal with classmates and faculty members on various situations.
My suggestion for you is, if it's grades that's discouraging you, than seek academic help ASAP, talk to faculty and professors, and perphaps use tutoring programs.
Also, you might think joining organizations will take your time away from your studies, but to the contrary, joining organization such as a dental fraternity, various clubs, and/or student groups will help you find a "shoulder" to lean on.
In my opinion, to succeed in dental school, you must find a balance between studies and life.
To relieve stress, things I do are:
lifting weights
listen to music
go out with classmates
go out on dates
watch reality TV shows
talk & communicate with classmates
talk & communicate with faculty
golfing
go to the beach
sleep
Hang in there my friend, you've made it this far! Things will eventually get easier!!