The thought is similar to John 14:27. Again Christ emphasises that what belongs to him is given to us.
It is Christ’s desire that we should be and remain happy believers. Is this a constant and unabating joy? No, ‘full’ does not mean it will be permanently with us. Some say we should always be happy and to fail to be so is a lack of faith, but this joy will not eclipse all pain, sorrow and grief. No, believers experience the sorrows common to all human beings, but underneath all of that is a rejoicing that God has redeemed us and none of these things ultimately harm us because we have a Saviour.