Mark 3:14 He appointed twelve that they might be with him and that he might send them out to preach
When Jesus chose the twelve disciples it was not a random choice of twelve people but a specific calling of those twelve men to do an appointed task.
When He says He has chosen us, as in yesterdays verse, it is not a random choice but a specific calling for us to do a chosen task!
Yes, God has already chosen us to do something and if we are willing to listen we will get to know what it is – but we need to listen!