And you have to give up being a football player:
Peter Knowles (born 30 September 1945 in Fitzwilliam, near Wakefield, Yorkshire) is an English former Wolves football player. He spent his career at Wolverhampton Wanderers, where he became a popular player scoring around 101 goals in all competitions. He voluntarily ended his football career in 1970 after he became one of Jehovah's Witnesses. He is the brother of fellow professional footballer Cyril Knowles, who even became so famous that he had a special song written about him: