To achieve amazing things, we have to push ourselves in ways we never though possible. Our minds must remain open to possibility and we have to allow, yes allow, ourselves to push harder than before. We have to believe we can do anything we want to accomplish, no matter what anyone else says or does. There can be no doubts or fears, only belief and drive.
Many people thought it impossible a human could run a 4 minute mile. Roger Bannister didn't listen to them and in 1954 did the impossible. This has now been done by many more people. What was once impossible is possible. Many people never thought a human would stand on the summit of Mount. Everest. This was before Edmund Hillary and Tenzing Norgay reached the summit in 1953. This has also been accomplished by many people since. What was once impossible is possible. We've put people in space and on the moon; we've created machines allowing people to stay under water for months; we can speak with anyone in the world instantaneously; we can fly; we can bring people back to life after death. All of this was accomplished because someone believed it could be done.
Creating amazing things isn't easy. Not everyone will do it. Most of us will never push ourselves beyond what we we think we can do. We won't really know what our limits are because we will never test them. Without pushing these limits, we won't do the impossible. What do you want to do? Besides your limiting doubts and lack of belief, what's stopping you? Stop doubting and start believing. Start doing. Your goal may not change the world, but getting there will change your world. What are you actually capable of doing?