Actually, I expect that they find a life without the excitement, the thrill, of constant adrenalin very difficult to deal with. Hence dicing with danger, or seeking some sort of edge (such as gambling), or feeling the need to constantly push themselves. Some of them clearly develop addictions - again, to substances that offer a permanent 'high'. Fast, expensive, powerful cars are only one symptom of such things.
For that matter, I seem to remember reading that Alex Ferguson used to like to see his players settled down into stable relationships, rather than drinking and night clubbing; it seems that he felt that a spouse and family served to ground them, stabilise them, and offer psychological security and stability and serve to help the players become more mature as human beings.
Sometimes, I have seen this same dynamic play out with colleagues with whom I have worked with in strange spots abroad; even though they are away from the situation of stress - and the satisfaction of dealing with extraordinary challenges and sometimes dangers - they also miss it and suffer from the withdrawal of the circumstances which gave rise to it.
