We Need to Talk
Breaking up with someone is never a pleasant experience, which is why people try to make the process less uncomfortable by adding humor to it. There are countless examples of people using similes and metaphors in their texts to break up with their partners, but this one is probably one of the best.
If you are one of those people who do pushups regularly, then you would understand what this person was trying to tell his girlfriend. Just like the pushups on knees, their relationship wasn’t working out and therefore had to end, one way or another.