50th birthday is special in the life of everyone because it is what we call the half milestone, when you have completed half a century of living on this earth. It is when you start feeling young even though your grand kid can ride the bicycle. This is the age when you look back on all the good things you have done and regret those things that you never did.
You have experience in your hand, and it is something a bright 20 year old will take 30 years to earn. And by 50 you have made a lot of contacts and have given out your share of favors and the time to call in those favors. It is a great feeling to be 50 and to reach there is an accomplishment itself which should be celebrated.