Never feel like your income is secure, you could be let go because of an instable economy, cutbacks, or whatever excuses you want to give us. Your boss is just waiting to fuck you up.
When things start to work out. When life is going good for once. When it seems like your problems are not getting better, but at least they're not getting worse either.
Don't buy it. Don't let your guard down. Because shit getting all warm and fuzzy is just life's way of softening you up for the ultimate sucker punch. Never forget that there's always a catch, a downside to every upside, and some downsides to spare after that. Even if they aren't immediately visible, they're there. And if you turn a blind eye, for even a moment, fate's gonna blindside you so hard that when you're extracting your wrecked corpus from the pavement, your brain will be screaming 'how the hell did I miss that, why the hell did I miss that?'
Now bear in mind I'm not saying you shouldn't enjoy the good parts of life. Hell, you should, you're missing an opportunity if you don't. I'm also not saying that fate is the great equalizer either, life is random and there's no reason that everyone's life has to come out even.
But it's because life is random that no matter how good it's looking, no matter how safe you feel, there is always, always potential for shit to go wrong. And to be mentally unprepared for shit to go wrong is to be devastated when it actually does. Don't let your self be unprepared, don't soften up. Never forget that the higher you are, the further you have to fall, and the harder you'll hit the ground. Never forget.
Never let your guard down.
Speaking from a perspective of lifelong paranoia, never letting your guard down is the fastest way to never enjoy anything.
Being less sensitive versus the issues in your life can make the bad times not as harmful while allowing you to relax every once in a while.