With work, it's very much the realisation that I am nothing but a number to my employer, therefore, they are nothing but a pay cheque to me. Everyone is replaceable, therefore, if shit hits the fan (and it's my fault), worst case scenario, I'm out of a job. So what, there are plenty more to go around (I work in a skills shortage area, though).
I am very good at compartmentalising, and that is a skill you can practise. If it is something I can do right now, I will, but if it has to wait until Monday, then fretting will just ruin my weekend and so I keep busy with fun stuff instead. There is a Japanese proverb I have internalised over the years: The time is the same whether you spend it laughing or crying.
I preempt as much as I can, too, and stay organised as much as is physically possible. Being organised often has the knock-on effect of feeling in control, and that, in turn, helps with lowering my stress levels.
Oh, and when I get home I have a comforting drink. Some days that's herbal tea, some days it's hot chocolate with cream and others it's whiskey straight from the bottle. But I have that drink to look forward to every day.