Exercise is good for you? Really?

I’ve recently begun running again and despite various aches and pains, have enjoyed the experience in a masochistic way. I enjoy being out of doors and on a work day, when the alternative is being closeted in front of my computer in a stuffy office, even when the weather is cool or windy, it’s always preferable.  Sadly, I don’t ever seem to get the post exercise high that many other people enjoy, so I’m probably not pushing myself enough but try telling that to my brain as my aged pelvis, hip and knee joints protest.  Now where are my trainers?