I very nearly quit doing my degree, sometimes I used to think "whats the point". I really enjoyed the course, but it was all the assignments, revision and reading that got to me. Now Im glad I didnt, and Im sure you'll feel the same after you graduate. If you are worried about letting other people down then try not to- afterall, you're the most important thing and you should do whats best for you. Stay positive and Im sure you will get the marks you need.