In "Ulysses," Ulysses shows a restlessness in the face of his advancing years, striving for one last energetic reclamation of his earlier glory. In many ways, this feels like a willful defiance of the aging process. In it, Tennyson is simultaneously looking backwards, towards the awareness of and celebration of past glories and triumphs, as well as forwards, towards the future, by way of this last journey Ulysses would embark upon, before eventually dying.
It's an interesting conundrum, because I feel like this poem celebrates a very specific kind of retirement: in it, Ulysses retires from his kingship, passes on his responsibilities to his son. It presents a very active, very energetic vision of retirement, through which Ulysses seeks to recapture something of the person he had been, back when he was younger.