Drawing has alot to do with believing in oneself. I hear many people before they even try to invest time into drawing say that they cannot draw. I believe that the only way you are going to improve your drawing skills is by spending alot of time drawing. Improving is not easy and takes alot of practice, but with lots of commitment I believe anyone can be a successful artist. If I didn't believe in myself I would not be drawing today. It may take years for someone to notice your work, but you will improve if you never give up. Sometimes even I become discouraged but I never give up drawing. I sometimes hear of people who are really good at drawing but give up later on in life because they feel as if they will never be as good as other artists and I feel this way at times too but I know that I have improved enough to continue, its a waist of time, or that drawing is a gift. I do believe that some people draw better than others simply because of their dedication to drawing. Believing in yourself will give you confidence and make it possible for you to improve and mature as an artist. Just don't give up because your not at the level of someone else.
It's nothing wrong with comparing your work with other artists who may be better skilled. This just helps you to become a stronger artist as well. Without confidence in oneself its very difficult to strive as an artist so always believe in yourself and others will believe in you too.
Drawing what you see is probably the most important advice any artist should know. If your not drawing what you are actually seeing then the subject you are drawing is not going be accurate and you are probably in many cases going to become frustrated and want to quit drawing altogether. Knowing how to draw proportions well takes time to master, but with much practice it can become second nature for anyone who has the desire and patience to draw for long periods of time. It took me forever to understand how to make drawing people easier for myself. I just didn't wake up knowing; I had to practice alot and honestly I still have alot of practicing to do; although I have improved alot over the years.
The artist who remains consistent draws without worry, and has excellent vision when it comes to perfecting the skill of sketching in a quick manner because he has a goal and is destined to reach it no matter how long it takes. I love timed sketches because they force you to draw as much as you can in a limited amount of time. Plus many people, including myself in such cases draw better under pressure. Light, quick strokes are the key to drawing fast while focusing on the subject you are drawing.
Drawing has alot to do with seeing than it does sketching lines on paper. A good artist trains oneself to see well understanding the movement of ones subject. The more you draw, the quicker you will become at it as goes for anything else you train for in life. Drawing is no different. Everyone has their own pace according to how one thinks. I, myself am a slow drawer who begins a drawing and may put it away for awhile only to come back to it another day after I have a brand new perspective of how I want the drawing to be. Some artists are fast drawers in which they begin a drawing and finish it within a few hours maybe in the same day or the next. If I am given a commission then I have no choice but to begin and finish a drawing, but when drawing my own personal pieces I usually take my time to make my next one better than my last best one.
Whether you want to be the kind of artist who finishes a drawing at a quick pace or a slow pace it is really up to you. As long as you are satisfied with what you finished drawing looks like and make a constant effort in improving is all that matters.