Cuchculan, it's so funny. I've had several conversations with my older sister which are almost verbatim to what you just said. She is of your opinion, lower your standards for life and everyone around you. It's better to be pleasantly surprised than horribly disappointed.
Although I do agree that this sounds like a much better way to live, it's not easy for me to see things that way. Growing up, I was always pushed to do better. If I got 65% on a test that was a failure, I should've gotten at least 75%. If I got 75%, well so what? Big deal, I could've gotten an 80%. So on and so forth. I get what my mother was trying to do... she wanted to make sure that my grades would be good enough to be able to get into a good university and get an education which would take me somewhere in life and make me tons of money so that I wouldn't have to struggle like she did.
But I got used to thinking that way. For me, I will never reach my goals because, by the time I get there, I've already raised the bar again. I work really hard and put a lot of time and effort into my job. I can see it paying off, but what's the price? Often my personal life suffers for it. And when I make a mistake (which has been happening lately, since I just got a promotion into a much more difficult role at work), I take it very hard. When I fail I talk myself down, like I wasn't good enough, maybe I'm not good enough for this job.
But then, when I look back months later I realize that it wasn't that big of a mistake. And not only that, but I learned from it! I've grown from every mistake I've ever made, and it's made me more successful at my job. And the same goes for personal life too.