Why We Do It ? Obsession ?

Here is a Vikram Seth Interview where he concedes that Obsession is what got him to write that huge novel "A Suitable Boy".

‘Obsession kept me going’: Writer Vikram Seth on 25 years of A Suitable Boy

We enter life and thus inherit
The kingdom of the human voice.
The Word is Word because we share it.
Wonder encourages our choice
To sort out life’s conflicting data,
To come to terms with its traumata,
To shape ourselves to nothing less
Than reasoned self-forgetfulness.
For years we’ve traded rhyme and measure,
And if our poems are books today,
It is in hopes that others may
Take from them solace, sense, or pleasure,
Though years pass with their wonted speed
And though the times we shared recede.​