Byron, though sometimes difficult to read, has that mysterious something that makes a reader remember and think about what he has to say. His poetry is powerful, and imagery more so.
"She walks in beauty" seems so simple upon first reading, his admiring tone so formal, as such an object of beauty can not be addressed more personally. But we get from this poem a deeper understanding of the mechanics of beauty as seen through the Nature-appreciating attitude of the speaker. The subject of the poem represents divine beauty, surpassing even that beauty which "heaven to gaudy day denies," meaning that she is a balance (all that's best of dark and bright..."). Her beauty comes from her calmness, her "days in goodness spent." I just think it's a great love poem.

In "So, we'll go no more a-roving", we have a writing about sorrow, written when he turned 29. In it, Byron opens by saying that while the world outside has not changed, (the heart be still as loving,/And the moon be still as bright...) something inside the speaker has. In the second stanza, he makes the point that the "soul outwears the breast," like repeated in and out of a sword in the sheath will wear out the sheath, because the sword,like the soul, is made of harder stuff than that which holds it. The "heart must pause to breathe, and love itself have rest", or it will destroy the body and mind. He seems to be saying that he recognizes his aging, and must rest, or risk running himself down. He ends on a sadder note, that he is giving up on loving, ("though the night was made for loving...we'll go no more a-roving by the light of the moon."), perhaps lamenting his womanizing, but definitely lamenting his loss of youth.

If you thought he was depressed at turning 29, read what he wrote when turning 37. He recognizes his age, and his loss of youthful charm, stating "Tis time this heart should be moved/since others it hath ceased to move...My days are in the yellow leaf...The worm, the canker, and the grief/are mine alone!" He wishes that someone would return his affection, seeming almost desperate to be loved and not alone, which we see from the first quote and when he says, "the fire that on my bosom preys/is lone as some volcanic isle." His desire for love has become "a chain" which oppresses him. He changes tone, though, and seems to be giving himself a sad little pep talk, comparing himself and his love life to that of a soldier. He mentions that he was slave to his own passions in his youth, comparing it to the conscription of a soldier with no option of retreat--"The Spartan borne upon his shield,was not more free." He encourages this "soldier", his spirit, to "track down" and destroy his passion, to which he should remain indifferent. He asks why he should live if he regrets his youth, and in keeping with the metaphor of the honorable soldier, decides to choose his place to die willingly. In these last lines you see him becoming more passionate, but less for love and life, and more for ending the pain of loneliness.
There is a lesson here on what happens if you spend your life in affairs--one day you wake up and find that you are alone, and because of your reputation, you remain so.