I'm doing my first year of engineering and I've noticed something: the people I help out with studies always get higher marks than me. I'm used to getting A's (though my marks didn't exceed 90%), so I think I'm quite good academically. Last week, I helped out a girl in computer programming, and she got 20/20 for that assignment while I got only 14/20. I'm not a really competitive guy now, I don't feel super jealous when I see other people getting higher marks than me. I wouldn't mind if I had obtained 18 or 19, but now I feel bad. I really want to get A's minimum, and I need more than 75% to get an A (I got 70% in that assignment). A week before that, I helped a guy for the physics homework, he obtained 8/10 while I got 7/10 (less than 75%, not A then). I feel really, really cheated. Am I being too helpful? Are people abusing me? I don't care if those people get ranked higher than me, I just want to get my A's.
In junior high, I was first in class, my marks were always 90+. I never helped people with assignments or anything. Okay, I was pretty much selfish, asocial, and arrogant. Now when I'm being nice and helpful, I feel cheated. And because I'm getting lower marks than the rest, I don't feel smart anymore. This is hurting my self-confidence. I'm not feeling like studying anymore.

People,your peers, are asking for your help because they think your smart and your methods are working!

Instead of doing it for nothing why not offer 'grinds' if its allowed, get paid for your effort!

There's a great teacher/mentor in you, it's a gift to be able to communicate the lessons to other people in a way they understand,and for them to achieve high marks is really a credit to your teaching ability.

You have a gift!

Try and turn around your thinking, your putting in the work, your efforts will reap rewards, perhaps not in the way you thought though.

OK, thank you for the piece of advice.
I explained my problem to a friend in civil engineering today, She suggested that I should explain the bare minimum, that I should not reveal everything, to keep a few tricks to myself. I think it's a dishonest and deceitful action. I mean, I don't care what marks my friends obtain, I'm only wondering how its possible that I'm not obtaining the marks I deserve. Why I'm obsessed with A's? Well, in my country, only students who graduate with First Class Honours can get a nice job in engineering right after university to pay back the students loans as quickly as possible.

I agree with redhed.

I too was always at the top of my class and agreed to help other students by tutoring, with projects, etc. I found that I have a gift for teaching and training which has come in handy for me in many ways and is far beyond my achievements in intellectual pursuits. Like redhed said, you have a gift. Many light bulbs have flashed on because of you.

Turn your tutoring into an economic effort, with payment asked or a bartering done. That would help yourself esteem and also enhance your reputation.