One word for the act of making a decision. Not looking back. Moving on
How about committed?
Meaning - to pledge (oneself) to a position on an issue or question; express (one's intention, feeling, etc.):
Asked if he was a candidate, he refused to commit himself.
The ability to do so is decisiveness (noun) and such a person can be called decisive (adjective).
1 The ability to make decisions quickly and effectively.
‘the crisis will require leadership and decisiveness to resolve it’
1.1 (of a person) having or showing the ability to make decisions quickly and effectively.
‘Like Clifford, he is decisive and very skilled at pushing agendas through.’