Second term presidents feel the need to explain themselves, often at length. Most second term inaugural speeches have been longer than the first and contain the word "I" many more times.
The notable exception was Abraham Lincoln, whose second inaugural was only 701 words and used the word "I" only once. (Somebody has actually done the analysis on this.) But Lincoln was exceptional in more ways than that, so let's count him as an outlier.
But why do second inaugural speeches tend to be a little defensive? Well, you get knocked around a lot in your first four years. The nature of the job, the nature of any public executive job, is to have to govern an entire country or state or city, which includes those who disagree with you. So, it's all but an ironclad rule that your most passionate supporters, who by nature will usually be your most ideologically pure as well, will be disappointed in your actual performance.
The top job requires the ability to compromise and demands that even dreamers get practical real quick. So, you find yourself explaining what parts of you that stood in that same spot four years ago remain intact and why you needed to change the way you did.
So, President Obama doesn't have to explain himself to me. I can relate to his experiences if you just substitute snow plowing for Afghanistan.
Still, like a lot of liberals I'm disappointed about a lot of things. I wish we had a more pure form of health care reform, that we had tackled global climate change, that the economic stimulus plan had been bigger and repeated, that it didn't take the murders of twenty little kids to get even kind of serious about gun control. I could go on.
On the other hand it would be a mistake to not count our blessings. We have a thoughtful and very intelligent president who thinks before he speaks, and speaks in complete English sentences that form coherent thoughts. (We forget there was a time when this wasn't always the case.)
We have a president who has carefully wound down two wars, improved health coverage for millions of Americans, guided the economy back towards sustained growth, moved along with the nation toward complete inclusion of gays and lesbians, saved the American auto companies and their jobs, and generally (with the big exception of climate change) done right by our environment.
To paraphrase Martin Luther King, the long arc of this administration is toward progress and toward justice. Is this president everything I hoped he would be? Of course not -- they never are because they can never be. But Barack Obama is a good and decent and intelligent man, cool-headed in a crisis, a man who loves his country, and is guiding it as best he can in polarized times and in a complex world.
I'm still glad and still proud that he's my president.