To some extent, that's okay. That's really who you are.
Are you an introvert? Don't force yourself to be extraverted. You cannot change it. Trying might even hurt you in the long run.
Are you great at music, but bad (or not passionate) with numbers? Don't force it as a career. If you're not really good with numbers, the best you can become is average. You cannot change it. Use that time to practice music instead. Who knows? You might become remarkable, one-of-a-kind, an outlier.
Instead of trying to change it (or fight it even), accept who you are. Embrace who you are. You do not have to conform to the world's standards. The world's standards tend to smooth out the edges, to control the outliers—the ones who stand out.
But, saying that you cannot change who you are is not okay when it's a form of hiding.
It's not okay when you're trying to correct a bad habit or an addiction.
It's not okay when changing yourself means becoming a better person.
It's not okay when you're just saying it as excuse.
It's not okay when you're just trying to avoid making an effort or working hard. It's probably just laziness. Another excuse. Another form of hiding.
In these cases, you can change who you are. No, you must change who you are. You're holding yourself back from achieving great things.
[31 Day Challenge Update] I forgot to post an update yesterday. But, yes. I wasn't able to get up at 4:30 AM yesterday. Today as well. I'll try to reset tomorrow.... again.