Think about it like this, at one time in our life, we all start out the same, as a blank slate. Some may grow to specialize in area A while others will specialize in area B. Some people can pick things up faster and some just need a little more time. When I started out I wasn't too confident as well, and a lot of my friends were really good, so I would always put my self down. I used to always compare my work to others, and if it didn't look as good I felt even worse.
Now when I see really good work, I use it as a goal, to improve to that level.
I know that it won't happen over night, or a year (depends on where you set the bar) but it's something to look forward too. 
Most of those amazing artists, draw a lot, and not just the same thing but different things, people objects, things in real life. Most of them also understand the basic structure of the human form, they know how bones are positioned, the shape of muscles, and basic proportions. And like all of us, started out with stick figures as a child, they just decided to continue drawing, while most of us don't.
It's ok to get frustrated, feel impatient, all of that. Look back at your older drawings, you may not see a difference right away, but I'm sure there was improvement, whether it be noticing/fixing mistakes, or becoming more comfortable with the media you use (pencil, paint...). Sometimes other people notice improvement more than yourself. Getting critiques from people can help sometimes, but it has to be constructive, useful, so that you can improve upon it.
All that and still the question isn't answered xD
Well when I have artist's block, watching tv/movies, listening to music, reading, video games, talking with friends, this art group, any sort of brain stimulation might work. Sometimes you just need to have a break from it and think of something else entirely. I had major artist's block when University became overwhelming, stress also does that.
so yea these are my thoughts,
If you guys wanna add to this, take away, or point out anything I said that doesn't sit right with you, go right ahead. Sometimes when I write things it doesn't come out the way I want it to, or it gets misinterpreted, or just anything lol
I am not confident in my writing skills,
and whoaa I wrote a lot haha 