As a Math teacher, I help make sure students graduate high school with skills to go to the next stage of their lives, whether trade school or college, or whatever.  Part of that is the assurance that, 'Yes, you can do it, and let me show you how'.   Mostly I don't know whether I succeed, but sometimes I hear good news from a former student.  I believe in "Yes, we can!" because it is much better than "No, we can't so we'd better not even try."

I think that was part of Obama's message, the belief in education and the ability to reach a goal if we are willing to work for it;  that whatever anyone plans to be, they should be the best possible for them.  He did not succeed as hoped in solving the problems he was handed, but he accomplished a lot.