I am ex air farce (rigger) and I think as others have alluded to - ex forces with a skill/trade/specialist knowledge should do ok in civvy street.
The company I work for employs fairly large numbers of ex forces - how they fare probably largely depends on their individual personalities rather than any forces skill set !
As others have alluded to - those with no trade/skills and or those with PTSD may well struggle and also as Thing posted - a percentage of those who struggle may well have done so anyway - with or without time in the forces