I didn’t understand Keats when I was 25. I was too strong, too healthy, too oblivious of my own mortality to understand the poetry of a man dying of tuberculosis. But now in middle age I finally understand what he felt when he saw the Elgin Marbles in the British Museum and fell into despair at the thought of the arc of history, something he could understand but never experience.
On Seeing the Elgin Marbles
By John Keats
My spirit is too weak—mortality
Weighs heavily on me like unwilling sleep,
And each imagined pinnacle and steep
Of godlike hardship tells me I must die
Like a sick eagle looking at the sky.
Yet ’tis a gentle luxury to weep
That I have not the cloudy winds to keep
Fresh for the opening of the morning’s eye.
Such dim-conceived glories of the brain
Bring round the heart an undescribable feud;
So do these wonders a most dizzy pain,
That mingles Grecian grandeur with the rude
Wasting of old time—with a billowy main—
A sun—a shadow of a magnitude.
Writers Without Money 
Bloody melancholy! I don’t want to die.
When I have Fears That I May Cease to Be
By John Keats
When I have fears that I may cease to be
Before my pen has gleaned my teeming brain,
Before high-pilèd books, in charactery,
Hold like rich garners the full ripened grain;
When I behold, upon the night’s starred face,
Huge cloudy symbols of a high romance,
And think that I may never live to trace
Their shadows with the magic hand of chance;
And when I feel, fair creature of an hour,
That I shall never look upon thee more,
Never have relish in the faery power
Of unreflecting love—then on the shore
Of the wide world I stand alone, and think
Till love and fame to nothingness do sink.
https://www.poetryfoundation.org/poems/44488/when-i-have-fears-that-i-may-cease-to-be
I used to read a lot of the Romantics (and the Symbolists and other related poets) in the 90s, when I was a teenager. Their lives and writing were my ideal for living (and dying), but I survived. I still read their works sometimes, but with less passion than in those times. But Keats always makes my heart run faster.
I didn’t get Keats when I was in my late teens and early 20s. Back then my favorite poet was A.E. Houseman. I’m not gay but his decades long agony of living unfulfilled in the closet after an unrequited crush on a classmate at Oxford just resonated with me. He’s also Morrisey’s favorite poet.
I haven’t read him, but I can relate with that kind of unrequited love. Strong stuff.