Do it matter if we pray with others and not privately? Granted it is a very good thing to gather with other Christians in order to pray. We should all be committed to this according to Acts 2.42. It is also vital that we pray privately. Jesus did make that clear in Matthew 6.6 when he instructed his followers to go into their rooms and shut the door in order to pray.
Charles Spurgeon said that private praying is the strength of the church: "Neglect of private prayer is the locust which devours the strength of the church"