One time in university I got a nasty stomach virus and, after days of weakness and eating jello, I finally ventured outside to walk to school.  I was so weak that half way there I had to stop and lean against a tree to rest.  That tree was so solid and so there.  That was the first time in my life that I realized how important it is to have something (and of course, more importantly) someone to lean on.  I also realized how important it is to lean.  Sometimes I forget, but the tree makes me remember.