Ah, main characters. A good one makes the book, a bad one ruins it.
And secondary characters are easier. Not that we should all dash around creating a two-dimensional, wise-cracking supporting cast, but when you don't have to probe someone's motives as much, it is easier to like them.
Main characters are nastier.
The main character in my current WIP is a fairly nice and fairly normal girl in her late twenties who fell backwards into a life-absorbing career, which she is pursuing to the detriment of everything else in her life. Sometimes I want to shake her, because we've all had that neglectful friend who doesn't bother calling for months but shows up when she needs someone, or when it is understood that you See Friends (birthdays, New Years', etc). My MC even has a little rant about this at one point, not seeing her own hypocrisy.
The main secondary character is her journo flatmate. Who would also drive me a bit nuts in real life. But I'm not spending as much time looking at her flaws, so she is much more likeable in the text.
How do we solve this and keep our MCs likeable?
I have no sodding idea. I find liking them myself helps. And I am trying to keep her active - so she is dealing with her own choices, rather than just reacting to external factors. Also, this where Beta readers really come into their own.