It’s when the rainbow fades and sparks disappear and the story of the relationship shuts down. Worst, life starts to get bitter between the lovers. We knew that saying “it’s not you, it’s me” was just one of the famous excuses for someone to get rid from the relationship and most people thought that it wasn’t fair for them while some thought it’s for the best.
This is happening to rare cases of relationship. Some couples just don’t realize yet what’s making them unhappy together thinking there’s nothing wrong. Some individuals are using this quote to ease the breakup. At first they were very happy, romantic and feeling that they were in a cloud9 and then one day, they get bored with each other, fight for small things and break up.
In my own opinion, it's when relationship routine gets its bad particular habit after falling to wrong person and was overworked and clichéd. This is due to lack of communication abilities and saying “It’s not you, it’s me” is keeping oneself accountable for his inability on making the other happy. It's a way of expressing that the he's a moron. It's hurting himself to hurt the other.
Sometimes, even to someone whose in pain upon break up, this is a way of sacrificing his happiness to make both lives better. This is a courageous act especially to couples who can’t be controlled because their lives were growing apart. We sometimes mislabel it as loves which isn't. The note “It’s not you, it’s me” has a deep meaning and it is up to us as to how we decide its meaning. However, if that someone is an asshole then you should have known it from the start that it was just temporary. If you're hurt after hearing those words, then you should allow time to heal. I suggest you endure the pain until you realize that you are hurting no more and you move on.