[reallydontask]

> Once you start doing the thing you were nervous about, it becomes much easier and less stressful.

This is not necessarily the case. Sometimes you lack confidence with good reason because you are (currently, potentially will always be) unsuited to the task at hand, so you become nervous and stressed. There is nothing wrong with this either. Sometimes, it is worthwhile to persevere other times it isn't.

The hard thing is to know when to persevere and when to quit.

[crusader1099]

Indeed. And I should probably have clarified in my comment that this method works for tasks for which you are too lazy, bored, or unmotivated to do, but you know that you could do them if you put your mind to it. Like you said, being too nervous to work on a particular task because of other reasons is a different experience altogether.