What to do when someone say I am a looser?

Empathy. Why are they saying that? Do they need to make themselves feel better by putting you down? Are they having a crappy day and taking it out on you?

People are not naturally cruel. There are reasons. If you look for those reasons it's much easier to understand why they would want to hurt you.

The trap here is that if you care about being called a loser, you have self doubt. That's fine, most people can improve in one way or another. But the kind of person who can accurately criticize, and helpfully criticize, is never the person who uses a dismissive term like loser.

Even if they are being cruel, they probably arn't being terribly creative about it. Go watch Full Metal Jacket and see how a real badass insults people.

Don't focus on doing only one thing. You can be average at doing something and great at something else. If you're only writing code, start doing something that's completely unrelated to computers, like handicrafts so that you have more than one metric by which people could (if they dare) judge you. A good metric to live by is how many smiles can you put on other people's faces around you. If you started some sort of handicraft, you could make cheap to manufacture, high emotional value gifts or products that others would love and if you can make other people happy and they like you back, you just have a legitimate reason to slap that person who called you a loser senseless next time he/she dares to say that again. Most important, live by your own standards and do more than one thing so that you have many standards.

"Loose" rhymes with "goose". It's the opposite of "Tight".

"Lose" rhymes with "news" and is the opposite of "Win". You probably mean "Lose".

Fuck what they think.

Harden the fuck up.