I think it's about a relationship that has ended, and one of the people is looking back on the relationship fondly, and isn't able to remember what made it so hard before. "I don't remember/just what made it so hard before"...and maybe he/she is realising the relationship wasn't that bad and is wants the other person back.
I think it's about a relationship that has ended, and one of the people is looking back on the relationship fondly, and isn't able to remember what made it so hard before. "I don't remember/just what made it so hard before"...and maybe he/she is realising the relationship wasn't that bad and is wants the other person back.