I would select the following lines from Act II scene i which indicate Othello's joy at his union with Desdemona, and yet his feeling is tinged with the strange foreboding that he will never be this happy in his life again -
If it were now to die,
'Twere now to be most happy; for I fear
My soul hath her content so absolute
That not another comfort like to this
Succeeds in unknown fate.
Secondly I would look at the intense emotion Othello feels when he has been convinced by Iago that Desdemona is unfaithful. In Act III scene iii Othello reveals his devastation in a vivid metaphor-
I had rather be a toad,
And live upon the vapor of a dungeon,
Than keep a corner in the thing I love
For others' uses.
By Act IV scene i we see Othello reduced to catilepsy as even his eloquent words fail him and he loses control of both his mind and body -
It is not words that shakes me thus. Pish! Noses, ears, and
lips. Is't possible? Confess?—Handkerchief?—O devil!
By the end of his life, Othello has reconciled himself to his failings and finally kills the only person he can truly blame for his thoughtless and violent reactions: himself-
Speak of me as I am; nothing extenuate,
Nor set down aught in malice. Then must you speak
Of one that loved not wisely but too well;
Of one not easily jealous, but, being wrought,
Perplex'd in the extreme; of one whose hand,
Like the base Indian, threw a pearl away
Richer than all his tribe;
Here Othello realises his fatal flaw, acknowledges it with dignity, then takes his own life.