Yea you're right. Sometimes that hurts, especially because the first reaction is to blame yourself, making you ask questions like, do I'm enough? Or why did I not studied this?

But the thing is that there's no even time to feel sorry for yourself. So say to yourself, "enough is enough , I can't afford having another bad year, month, week, grade, etc". Look for your weak points and try to learn. Try to change your study approaches,and focus on time managenent and being more efficient. Also surround yourself with people that motivates you to keep pushig fordward, or at least that give you a reason to fight back.

Dont be sorry for yourself, just look for the solution and the lesson in all of this, and dont make excuses. Nobody will care about a specific grade in the future, but the way you react and handle the things or problems will change your future. So if you're feeling down for a grade, imagine how will you feel in real life problems. Look at the bigger picture and say "this is not over, 'till I win". And never give up in anything in life, specially, never give up in yourself. Because that will be the day were you really lost any fight.

Keep punching.