Commitment/Resolution/dedication

Today while i was in gym i was thinking about the people who are dedicated to gym-ming. Then i recalled my previous experiences and came to a conclusion. A person who makes commitment only to himself is able to do that thing.. It should not be from outside, but the dedication should be from the inside. for eg. If i have decided not to do a thing xyz, i should be determined from inside that i will not do that thing xyz, rather than opening my mouth and speaking it aloud in front of everyone. I should be sincere to myself and this is the best way to fulfill a resolution..