Is it possible for someone to be in a relationship if they hate who they are? Conventional wisdom would say no... Love yourself first. You can't love someone else until you love yourself first. But how true is this really? It sounds like it should be true, but it seems like so many people harbor some self-hatred these days. Is it fair to ask them to deny themselves friends or dates or other love connections? I say no. It's neither fair nor necessary. It is totally possible to have a relationship without loving yourself first but you need trust and grit to make it work.
From my experience, those who are the hardest on themselves often are the people who can love others with all their heart. There is a difference between self-loathing and the inability to love. One is directed solely at the self, while the latter would define a hardcore psychopath. Clearly, there is a difference between the two. And to play at the other extreme, narcissists love themselves plenty but how capable are they of loving others?
Don't get me wrong, I'm not trying to completely debunk conventional wisdom. It does ring true in cases where people allow others to treat them poorly and give them the power to determine their self-worth. In these cases, yes, a lack of self-love and respect was their downfall. However, not all people are cruel and take advantage of others.
This is where my opinion comes in. Say a guy hates himself but he's in a relationship where he can be honest with his significant other (S.O.) about it. Perhaps the S.O. can work with him so he doesn't fall into the trap of second-guessing the relationship because he feels unlovable. But this requires trust. He has to trust his S.O. other enough that it forces him to challenge his self-defeating thoughts.
Of course like anything this is not foolproof. The self-hater has to be in a position where he wants to change for this to work and the S.O. has to be careful to only be supportive and not an enabler. Nevertheless, this definitely puts a pin in the inflated idea that to love another one has to love himself first.