You have sworn an oath either to a person or institution and you are sworn to uphold it. There is no coercion involved. You have taken this oath out of free will. The value of the trait determines how much of your life is consumed by the oath.
-1: An oath that is more a promise to once repay a favor.
-2: This oath covers an occasional event, but it is of such importance that your life might depend on it.
-3: An important oath that takes up much of your life and could limit your freedom. Akin to the knight's oath to obey and protect their master.
-4: This oath is all encompassing and claims more or less your entire life. A monk's vow to live his life in service to his god in a monastery, for instance.