Most of my inspiration actually comes from people-watching; eavesdropping is very useful too. Humans of New York is a wonderful, inspiring website as well, and of course books, movies, other poems, etc, provide plenty of ideas.
As for my advice: that’s a very common feeling for writers, to have very little confidence in their work. I don’t think you can ever really fully overcome it, but it helps to stop comparing yourself to other writers by saying: “This part of my writing is so bad, but this part of theirs is so good.” Instead, say “This part of my writing may seem so bad, and theirs may seem so good, so what’s the difference between the two? Why is theirs good compared to mine, and how do I fix that? How do I improve the bad parts of mine to make them more like the good parts of theirs?”
Change your way of thinking, and that will often change your writing drastically for the better.