When you always accept challenges, regardless of whether they are put up by yourself or proposed by others, you care to try and accomplish all of them.
Keep in mind though that, especially when you are competative, driven and hungry for victory, you might start to take on more and more challenges. Some might become a formality rather than a challenge, making it harder and harder for you to focus and accomplish what you strive for.
The biggest danger in this is that as you start losing your focus, and your number of challenges continuously increases, you might start to pay attention more and more to the challenges that you do not accomplish. Especially if your regular accomplishments, however great, become mundane to yourself.
Take a small step back every once in a while to see what you have accomplished and will accomplish in the future, rather than always having the negatives in your mind.