You've got an excellent question and I've got an excellent answer for you: https://www.youtube.com/watch?v=jTYkdEU_B4o It's a short video, but I highly recommend it to you (skip the first minute or so for a short historical intro). Please come back here and let me know if it answered your question. I also hope it doesn't just answer your question, but sets in your in a different mode for thinking, mode in which problems that seemed unsolvable can now be solved.