The thing about betrayal is that you never quite trust the perpetrator again. Sure, you may be able to sit across a table from them and smile neutrally or resist the urge to assassinate their character.
Still, there is always a sense that you can never fully trust them again...not in the same way as you once did. There will always be an asterisk by their name in your Trust Hall Of Fame.
Once the trust has faded, what are you left with?
A low level of anxiety and the inevitability that they will betray you again and it will hurt much worse the next time around.
Why will the next time hurt worse?
Because, you know now what they are capable of and still you stayed... hope clinging to the walls of your heart.