Keeping methods short by doing one thing means that you're able to write more maintainable, composable and readable code. This relieves stress in yourself and others and will lead to a happier, healthier life. There are a lot more resources for clean code out there - have a google some time. "Clean Code" and "Code Complete" are some of my favourites.
Heads up: As with any terse bit of advice, there will be exceptions of course, and subtleties and nuance that can't possibly be captured in a Byte of Wisdom. This has been what I've experienced, I'd love to hear yours in the comments too!
You can catch up with all the other bytes at http://bytesofwisdom.com/