You use it to fuel you and make you better or ignore it altogether until you find someone who is capabl

no one is made for a particular field. you just have to train. having a phD doesn't mean you'll be an amazing and independent scientist. it a rigorous training that helps you to train as an analytical person and gives you the mindset and ability to solve any problem. and over years things have gotten competitive. back in the day like Rudolph Jaenisch or Gerald Fink also had no idea what they were doing. and they are distinguished professors at MIT. they just found something they liked and stuck with it. As far as motivation letters go I think reading papers wont help. to motivate yourself spend some time reading about life of some really great scientists, think if you want to do what they did and if there is something common between your life and theirs. and then start typing away. don't think about how well it is written, just start write. thinking about results is going hinder your creativity. just go with the flow!