Desire

Speak for yourself.

I am speaking for myself.
But I am not the only one who goes through this.

Understood, but the way you're writing, it's as if it's a universal.

It's not.

Perhaps you mean
"Once I get something I always wanted to get,
I lose interest in it.
Why?"

This song is by Steve Goodman and appears on the album Somebody Else's Troubles (1972). Judy Collins sang it most beautifully...

"The Lovin' of the Game"

I saw the feather river glide over shining golden sand,
Struck a silver ribbon wide, held a million in my hand.
But beside the lookin' for, well the findin' is always tame
And there's nothing drives a gambler like the lovin' of the game.

All my life I ran around searching hard from town to town
But I never ever found anything to tie me down.
Still I wouldn't trade my time for a solid diamond claim
No, I would not trade a fortune for the lovin' of the game.

So long, darling, don't you cry, I hope that things pan out for you,
All the good times going by, got to have ourselves a few.
Where I'm going has no end, what I'm seeking has no name.
No, the treasure's not the takin', it's the lovin' of the game.
No, the treasure's not the takin', it's the lovin' of the game.

Want on.

We desire to acquire.

It is not an invariable rule that we lose interest in something once we have obtained it. Or perhaps I mean that not everyone is like that.