Not uncommon for these types to have some type of dependency issue. Usually its alcohol.
Regarding UFC pay vs Special Forces pay, someone earlier posted SF get paid more and that's why they don't go into UFC. Not true. Average salary range (depending on rank and time served) is $45-75,000 (higher end being 20yrs plus service). Where most of these guys make REAL money is in private contracting / security. They can easily make double or even triple the salary in just a few months on some contracts.
Mercenary pay is top $$$ ...risk is out of this world though. You basically have to be ok with suicidal situations.