I can define me in only three words: strong willed person. Most people consider it as a negative ability but I don´t think exactly in the same way.
This strange ability, which only a few people have, can help you a lot during all your live. First of all, you are completely decided to get your objective and you never give up. Moreover you always keep improving yourself. For example, since I was in the high-school I have always fixed a target to study, so I do my best to achieve it. This is really important and useful because you always have a motivation.
Obviously, it isn't always good, you have to be responsible and conscious of your real possibilities. You should not fixed any objective you know you can not achieve, because it can be dangerous. The reason is that you feel you have let yourself down for not doing it and you are less self confident. So it is really important to know about your capacities.
On the whole, I would say it has more benefits than drawbacks, and I am really grateful to have this great quality. But it is up to you, isn't it?