The speaker of the "Ode on Melancholy" is a bit different from the speakers of Keats's other odes. For starters, he urges us to take action rather than to sit back and contemplate something (like the "Grecian Urn" or the "Nightingale"). He wants us to embrace our melancholy and to use it, and he's got some strongly held opinions about how we should go about doing that. In fact, he's a pretty forceful guy when you get down to it—the poem opens with him saying, "No, no!" as though the reader were doing something wrong that the speaker wanted to correct.
As the poem progresses, the speaker moves from telling us what not to do, to telling us what we should do instead, and finally gives us his reasons. Sounds like he's covered his bases. But one thing that this speaker leaves out is his own experience. He's so busy telling us, the readers, how we should embrace melancholy that he fails to describe any experience with melancholy of his own. All of his examples and reasons are universal, rather than personal. Why do you think that is? Keats had plenty of experience with melancholy in his own life—why does he not reference it explicitly? How might that have changed the poem?