I've stated it in other posts before, but it bears elaborating because I know it's something that many of us struggle with.
I, by nature, am not a very confident person.
To the point that my confidence wavers on the most simple and sometimes trivial decisions, the list of examples of which would be too long to post here. To contrast, my wife is the kind of person who can confidently and, for the most part, decisively make a choice without feeling like she's stuck between a rock and a hard place; in essence my wife knows how to make an executive decision. I, on the other hand, I sometimes can barely decide how to take practical steps to plan my day unless there's a plan laid out before me already.
So why in the heck did I become a writer?
Plain and simple, I love it, which is really one of the primary reasons you should do anything (even when doing what you love feels like agony sometimes). Second, after reading things that I wrote, a number of people ranging from teachers to family members kept telling me that I had a gift and should pursue it. It took years, but I eventually started buying what everyone was selling, and while I knew that I wanted to write, I had no idea how I was going to pull it off. Well, after almost a decade of dilly-dally, finally self-publishing my first novel and a pleasant buzz and response following, one thing I've learned is this...
...I'm still not entirely sure how I'm going to pull this off.
I'm confident that God wants me to be a writer, and that He wants me to create fictional stories that reflect His Love, Power and Grace. Beyond that, the mechanics of achieving this in the form of a career are still a little on the fuzzy side.
I critique my own work harshly-- sometimes I even wonder if I'm cut out to do this. But then I remember that God doesn't give useless gifts, and He certainly doesn't like to see gifts wasted (like salvation, but that's another post entirely).
Am I going to be the next great American writer? I tend to doubt it, but can I become a great writer? I get the feeling that it's within my scope of accomplishing. And, if I can become a great writer, then who knows what else I can be great at-- the sky is virtually the limit, if you choose to look at that way. Either that or you can reject the construct of limits altogether, which I personally think is the best way to go.
Doubts and questions are going to come knocking regarding your abilities, however great they may be. But if you are confident that you were meant to do a specific thing and you have gotten more than enough confirmation that it is, well then those
doubts and questions should only thicken your skin and strengthen your resolve. Even if a majority tells you that you don't have what it takes, then you have every right to prove them wrong. In fact, you should consider yourself obligated.
Don't worry if you're not oozing confidence right now-- you'll catch it in time, especially as you embrace your God-given gifting. Trust that He gave you whatever talent or gift for a reason, and then use it in whatever capacity you can right now, then watch as that capacity grows.