I heard this once and it will be with me forever. To me the most painful experience in the whole world is thinking about myself as an old woman wishing I had experienced something that I was either too lazy or too scared to do. Do you want to be that person that lives vicariously through your children because you never achieved your own dreams? I saw that a lot in the pageant world when I was Miss Rodeo Montana. What holds people back from what they want to do deep down? I believe it is more discomfort than fear of rejection, even though both are common. It's uncomfortable to make the phone calls, write the letters, and put yourself out there when you are stepping closer to your goals. But the pleasure of long term success must outweigh the short term discomfort.
If fear is what holds you back, you must get aggressive with your goals. Rejection is great. It's an awesome thing because every time you are rejected and improve, then try again you are getting closer. I used to be worried to try things when I was training horses because I didn't want to make a mistake. One of Australian horse trainer Clinton Anderson's favorite one-liners is "Mistakes are good". Don't be scared to make mistakes. They will just make you better.
Don't be the person that looks upon others living their dreams with jealousy. Visualize yourself as an old grandma or grandpa looking back at your life. If you would say, "I wish I did that", go do it now!!! Err on the side of doing too much!