Instead of gazing adoringly at his face, you start counting the dark hairs up his nose. One day you're on the floor giggling at his jokes, next day you're on the floor niggling at his dirty socks.
You used to think he was broody and daring. You realise he was just moody and uncaring.
For the record, I am not talking about my current partner of course. But other relationships.
Like me and John.
Once I was adoring. John could do no wrong. We shared special moments together. Well, okay, just two.
One at a Katy Perry concert where he was sitting a few seats away from me. And another at a retirement village he opened here in Tauranga.
He posed for selfies. He chatted with my kids. He smiled at me. He put his arms round me warmly. I geeked out. I hugged the Prime Minister and I liked it.
John Key, it wasn't just your selfie poses that got me. You seemed to believe in the things that I believed in. I kind of liked what you were doing for the country. You seemed to know your stuff economy wise. Despite your background as a high-earning money trader, you came across like a down-to-earth guy.
The self-made millionaire who grew up on the mean streets. Being a big brand shopper, I bought yours in spades.
The country was booming, house prices soaring again. Jobs aplenty. People were even coming back from Australia.
It wasn't just me who put you on a pedestal. Pundits and polls said you had swayed many female voters. One survey had you as New Zealand's sexiest politician.
You overcame national disaster. Not just the Christchurch earthquake but other potential devastation. The global economic crisis, the Dirty Politics scandal.
You survived the fallout from Judith's Chinese adventures and eventually bounced Kim Dotcom off the front pages.
The country voted you back for a third term. People started to refer to you as the most popular New Zealand Prime Minister ever.
University of Auckland politics and international relations associate professor Jennifer Lees-Marshment said after the last election that you had won over the public with your "unique, informal communication style" which had branded you as having a positive relationship with New Zealanders.
It was this that helped you sail through controversies which never seemed to damage you in the personal opinion polls.
But were cracks starting to show back then? Lees-Marshment also warned Key's greatest enemy lay within.
After the election, she told NZME. that "complacency and arrogance" could lead to the eventual downfall of the party and Key needed to address this.
And it is not hard being a heart-throb when your competition barely seems to have a heartbeat. Phil Goff, David Shearer, David Cunliffe were all a bit blah.
Then along came Andrew Little. Winston rose from the ashes.
As early as February, polls started showing that more than half of voters thought Little was potentially a better match for Prime Minister John Key than his Labour Party leader predecessors. Last month Winston wiped up in Northland.
So am I down tooling my pompoms?
You started to do things that made me think about it. It wasn't the big things that others were raving about, like Sabin and the SIS.
It was the things that matter to me. Hiring more spin doctors. Sending soldiers to Iraq. Dismissing hungry kids in schools. Wading in on the Campbell Live saga saying people preferred light-hearted entertainment. Downplaying the Reserve Bank's warning about a housing bubble.
We'd been through a lot. I even forgave you for wearing white gym sneakers with dad jeans. Maybe we could get through this.
Then this week it all changed for me. Over something so stupid. Another girl's hair, which bizarrely you liked to pull. Which you kept on pulling, even though others, including your wife, asked you to stop.
Will this affect your brand? Will female voters be swayed?
I don't think it makes you a bully - it isn't as if you were descalping her. I don't even think it was that terrible. Not the abuse of power the opposition will try to make it.
I don't think you are a creep. You meant it as fooling around but she didn't like it. Now you admit you were wrong. And that's okay. We all behave like a jerk sometimes in social situations.
I'm not writing my Dear John letter ... yet.
