I recently heard a comedian say that while his real life seems to be getting worse and worse, he's killing it on Facebook.
The joke is funny because it's kind of true.
We all have a window-dressing aspect to our lives which is carefully curated to lure in potential jobs, customers, lovers, friends, cool kids, opportunities, or desired experiences. But our window dressing often only displays our latest styles and finer qualities. The good stuff.
That's why, no matter what the first impression looks like, it always takes time to truly get to know someone. And later on, if we get upset with that someone because they "let us down," it just means we're still locked on to the fantasy window-dressing version of that person or experience.
To flip it, try viewing a let-down moment as an opportunity (and even a privilege) to really get to know the other person in an intimate way that most people who merely pass by the window will never see.