A Loser is a person who doesn’t win for whatever reason. Harm can be done if people are unrealistically branded losers and lose confidence that they can succeed. A good example of a loser would be Mitt Romney.
Romney Took defeat really hard but he picked himself up and went into the hotel industry where he could succeed.
The loser has, above all, a fatalistic attitude about life. It's as if other forces are determining everything. The "other forces" may be supernatural, political-social, or emotionally vague (usually the last). The unhappiness that follows stems from this error. 
To avoid becoming a loser you should set realistic goals and get confidence in yourself.
This section adapted from WikiHowEdit
If you consider yourself a loser or others have told you that you are a loser, there are some very simple ways to change that. You don't have to be in pain everyday, you don't have to just get by. You can play to win instantly!
- Don't be a geek and do everything straight.
- Make sure that you don't wear horrible clothes.
- Don't make yourself feel like a loser.
- Don't let people make you feel like a loser.
- If you like anyone and they think you are a loser show them they are wrong. Then get a better person as a friend.
- Do not accept anything remotely like the above!
- Don't whine and cry that this is just the way life is for you because the Source (Universe, God, Jesus, Buddha, whatever name is comfortable for you) hears you and hears that you accept this way of life. Instead work to change things and stop being in pain.
- Make a decision. Make a decision to get out of what causes you pain. No matter how bad life is for you, thousands perhaps millions on this earth are in a worse position. And thousands like you have made a decision to change their lot in life and have succeeded. You can too!
- Commit to the following:
- Think like a winner. Put yourself in the mindset of a winner right now. Think only the thoughts that a winner would think.
- Visualize being the person you want to be, having what you want to have and doing what you want to do and think only the thoughts of being, doing, having everything that person is.
- Speak only the words your winner speaks. Don't commiserate with other losers, don't agree when other people speak negatively. There is value in everything if you look for it, especially if you learn from it. Speaking like a winner raises you up, everything else tears you down.
- Use your words to create good things, great things that make you and people around you feel good.
- Act like that winner! Winners don't bury themselves in front of the TV watching hour after hour of mindless junk that does absolutely nothing but show the worst of humanity. Winners don't listen to hours of radio talk shows that put fellow human beings down. Get out and volunteer to help someone, winners do lots of that.
- Sign up for a course that will teach you something worthwhile, perform several random acts of kindness every day, winners do these things.
- Before you know it, even instantly, the Source will have heard you and things will come into your life that will help you think, speak and act like a winner even more.
- Write down the steps you can take to make changes such as things you need to do or do differently i.e: stop smoking, start saving some money even if it is just spare change, turn off the TV and read inspiring books from the library. In fact spend a whole day in the library exploring the pot of gold that is in there for you!
- Ask the Source for help, it will come.
- When your life takes a turn for the better, and it will, tell others how you did it and encourage others to follow you.
- You simply have to just show up. 80% of success is showing up. The other 20% of success is what you do after you show up.
- Play to win.