Etymologically, a decision is:
A noun of action from past-participle stem of decidere “to decide, determine,” literally “to cut off,” from de “off” (see de-) + caedere “to cut.”
etymologyonline.com
Whereas a commitment, based on the word commit, means:
“To give in charge, entrust,” from Latin committere “to unite, connect, combine; to bring together,” from com “with, together” (see com-) + mittere “to release, let go; send, throw.”
etymologyonline.com
For me, a decision has more vigor than a commitment, and, therefore, it is my word of choice for my own goals.