Drawing what you are best at is a good option for those who are stuck drawing the same thing, realise this truth and stick to what you know. I myself draw in a comic book style and have become stuck drawing this way, but I am branching out by drawing in a cartoon style too and also trying to draw and even paint some fantasy art (coming soon in the form of a few video tutorials as I learn along the way myself.)
To draw what you are best at is a good idea, as you can become the expert in your field drawing the stuff that people will come to know you for and so with this comes a great amount of critism that this is all you can draw, but do stand your ground as others are only out to make themselves feel better by putting you down. Of course there is no harm in learning other styles of drawing and this type of thing as every artist learns in there own way.
But really an artist is remembered for creating one or two types of art and that becomes their trademark in their artistic field, so you don't have to worry about the bigger picture to start with, just pratice drawing and creating what you really like creating as this is one of the best bits of advice I can give you.
Although I'm not a professional artist in the sense that I don't have any books or anything like that out yet, but I have practised my art and honed my skills over the years with drawing tattoos and fantasy art and some comic book art which also I have coming up with some posts about drawing comic book stuff which I hope you'll enjoy.
Currently I am working on improving more on my art and that is the learning process that you should be taking yourself, draw other stuff to learn, but never lose sight of the best stuff that you can draw, because you will become well known for it.
Have fun drawing people and I'll have some interesting posts coming along quite soon.