"I'm not good enough."
"I can't do that."
"I'll never make it."
"I don't know where to start."
An additional debilitating condition is when you view works upon works and start to get overly critical. You view these images and ask yourself:
"why do people buy these images?"
"These images aren't that good. How does this person make it?"
"That's not art. I can create a better piece than that."
Stop it! Stop the negativity. You are only hurting yourself.
If any of the quotes sound familiar, it's time to get off the computer, shut the books, and pick up your tools and equipment. Don't worry about what others will think. Create art for yourself. Believe in yourself and your artistic vision. Don't worry about what is successful and why can't you make it when you think you are better. It's destructive behavior. Art is subjective and it appeals to people in different ways.
The more you create, the more you can draw inspiration from your own work, study your own work, and improve your own work. As you produce art, your technique will improve. But if you continue to mire yourself in everyone else's work, if you continue to be negative about yourself and others, and if you don't start producing your art, you will never create anything.
It is beneficial to study others works and draw inspiration, but it is also important to withdraw from that, draw inspiration from everything around you and from within yourself and create your own piece. There is no original theme or concept. What you should do is make that theme or concept uniquely yours, through your style, your storytelling, and your experiences.