What he's saying is...

David Foster Wallace addressed the graduating class of Kenyon College in 2005, and committed suicide in 2008. The latter act has, retrospectively, given the former a significance it would not otherwise have had. Commencement talks are usually as perishable as wedding toasts, and for similar reasons―should they survive―take on ironical color over the years. This particular talk actually went viral, I suppose because of the following:

It is not the least bit coincidental that adults who commit suicide with firearms almost always shoot themselves in: the head. They shoot the terrible master. And the truth is that most of these suicides are actually dead long before they pull the trigger.

Poor DFW! Some Stephen Covey, some Anthony Robbins he is. (Whoops! Was.) Ah, the irony. Or, worse: how pathetic.

But, no, I think not. Irony is found in a―sometimes subtle―disjunction between assumptions and actuality, patheticness (yes, there is such a word) in a patent disjunction between ambition and actuality. If the Upbeat-Speech-and-Later-Suicide were an ironic arc, then DFW would have been, in the speech, an inspirational speaker who, by his suicide, showed he never took his own advice. If the USaLS were simply pathetic, he would have believed that those stretching exercises for a healthy mind could cure his.

But neither color really sticks: in fact DFW knew he was walking in the darkness, and his own case was far more desperate than these freshly-scrubbed grads would know. His advice was pretty much what it seemed to be: how can you enlarge your mind in a world that has made adulthood a series of trivial trials and petty annoyances? But remember:

Again, please don't think that I'm giving you moral advice, or that I'm saying you are supposed to think this way, or that anyone expects you to just automatically do it. Because it's hard. It takes will and effort, and if you are like me, some days you won't be able to do it, or you just flat out won't want to.

DFW was asking these normal kids to take their perceptions out for a stroll, or even a vacation, once in a while. But he very well knew that at some point his own terrible master might make him climb Mont Blanc in his pajamas. For the moment he let that go, and simply spoke of sanity and kindness in a world that conspires against them.

The bushman treks many a dusty mile
intent upon the spoor of a giraffe.
He does not think about his weary life,
but slowly trots with an expectant smile.
However, should the missionary’s wife
have waiting by the wayside food and drink
he might just stop and munch a spicy roll,
and that subversion of his single goal
might wake him from his trance and make him think
about the empty end of all his strife.
Then all his living ties break link by link
as easily as that. The sun would sink
and throw his shadow as he stood there still;
the moon outline his figure on the hill.