Obsession

ob.ses.sion

1. a persistent disturbing preoccupation with an often unreasonable idea or feeling; broadly : compelling motivation

<an obsession with profits>

2. something that causes an obsession

- ob.ses.sion.al

- ob.ses.sion.al.ly

To put it to use:

She has an obsession with everything unachievable. 

The first known use of the word obsession was in the year 1680.

See also:

fetish, mania, fixation, preoccupation, preposession

And ladies and gentlemen, this is our Every day Word of the Day. Also because, this is so me right. Obsessing.