A person is a free moral agent whom God created with full freedom to make choices. God always encourages people to make the best choices but He will never override their free will. However, fundamental changes in people's long-term attitudes and life styles have always required persistent prayer over weeks or months. This is not because faith hasn't been strong enough but because God has to give people lots of time and space to go through changes gradually at the pace they choose or can handle. I think this is why pastors usually end up becoming very mellow fellows who stick with things long term without getting ruffled by set backs.
Pastors have to spend hours each week interceding for the members of their flock.
Yet they usually don't see the results of that intercession until months later. Before we start praying for people we have always got to examine our love walk. This is because we want to pray in faith but faith always works by love. We've got to make sure we're operating in love when we pray. The best way to do this is to open your Bible to 1 Corinthians 13 and read verses 4-8.