As I've grown up, now at 40 I understand more things about the world. In the case of private companies, I learned long ago not to get enamoured with them. Unless I am the owner, I work only for my paycheck. I've been in great companies, and some of them have paid me dearly. And I will always do my best for what I am paid.
But long gone are my days of pushing myself even sacrificing my health, family relationships and personal wellbeing for a company. In the end, they can and will fire me tomorrow if it improves the bottom line.