Learn to draw what you see. This is one of the most important steps to becoming a skilled artist. Who would want you to do a portrait of them, or a sketch of their favourite place if what you draw isn't actually what you see? Don't fret too much--loads of people make this mistake at times, and it CAN be corrected. Don't be afraid to really draw what you see. Sometimes, when you do start drawing what you see, the beginning of the sketch can look pretty awful--but it can turn out absolutely amazing. So do it. The next time you draw someone, really draw their face shape, their real nose, real eyes, real teeth. It'll take practice, but it's worth it.
For more you can refer to this site.