Udyapan is the time when you end your fast. After keeping a fast say for 16 Weeks then on the 17th week you do the Udyapan, in which you make the things appropriate for the fast and give to a pandit and seek his blessings for early fulfillment of desires. So if you do 16 Mondays fast then on 17th Monday you do the Udyapan to complete the fast. You may speak with a local pandit in a closeby temple who will tell you exactly the procedure that you are supposed to follow. Visit temple every Mondays it will bring you enternal happiness and keep you relaxed. You should go and thank God for all His Kindness and seek His Blessings.