I was also given two other valuable pieces of advice.
1. try asking the 5 whys [1]. for those that don't know it's basically a simple technique to find out why people do the things they do. it doesn't have to be a good reason, but most of the times it's not a malicious reason why people do things. sometimes though it's malicious. you should be wary of those people.
2. don't marry your job. there's no point getting emotional about things you don't own. in the end you own the things you do in your free time and what you get paid for is your job. so if someone does an incredibly stupid decision, it's their problem.
in practice though, i have problems not getting emotional when people are trying to do incredibly stupid decisions.
http://en.wikipedia.org/wiki/5_Whys
edit: added google cache link http://webcache.googleusercontent.com/search?q=cache:pyskool...