Both Homer and Tennyson portray Odysseus/Ulysses as an adventurer, but Tennyson takes up the story after the hero has returned to his native land and has been living a life of relative inactivity. Tennyson's Ulysses gives indications that he wants to return to the adventurous life of Homer's Odysseus.
Although Tennyson's poem, finished in 1833, is usually seen as having much to do with the death of the poet's friend Henry Hallam, the poem might also reflect some of the feelings of Tennyson's fellow countrymen about how their nation had fared over the past few decades.
British success during Tennyson's lifetime waxed and waned. The British has lost America in the Revolutionary War and they struggled with limited success against the Spanish and French. Their assault on the Spanish port of Tenerife in 1797 ended in a disasterous defeat, as did their efforts to take over the Platte River area in South America in 1806-1807. The next few years, though, saw an upswing of British success in Java (1811), Singapore (1819), Malacca (1826), and Burma (1826).
Such setbacks and successes might well be reflected in the closing lines of Tennyson's poem:
Though much is taken, much abides; and though
We are not now that strength which in the old days
Moved earth and heaven; that which we are, we are,
One equal-temper of heroic hearts,
Made weak by time and fate, but strong in will
To strive, to seek, to find, and not to yield.