Charles Conwell has vowed to use Patrick Day as motivation to become world champion as his fellow American fights for his life after suffering a traumatic brain injury in their bout on Saturday.Day was knocked out by Conwell in the 10th round of the super welterweight fight in Chicago and remains in an "extremely critical condition" in Northwestern Memorial Hospital following emergency surgery on Sunday.Conwell has written a poignant letter to his fellow American, stating it will be the last time he comments on the situation out of respect for Day's family and friends, himself and the sport of boxing.