This happens to me a lot and I know I'm not alone in this ridiculous belief.
Imagine the scene, you're reading a friend's social media post (because frankly that's how most of us communicate with friends these days), or you're actually talking in person. They talk about how they had been let down by someone and, like a flick of the switch in the self-deprecating part of our psyche, your immediate reaction is "Was it me? Oh, no... it was me wasn't it... I've forgotten to do something... It must be me".
And, even after a swift sift through your recent interactions you cannot for the life of you remember committing to anything, it remains like a solid heffalump of woozelness squashing your sense of self-worth and convincing of the shocking nature of your interpersonal skills.
You leave the post convinced you are a terrible person. After all, not only have you omitted from helping a friend in need but you've completely emptied your memory of offering to do so in the first place. Seriously what kind of friend are you?
You pen a quick note in panic, begging for forgiveness and offering to make up all ills whilst your subconscious bangs her head against the desk and calls you a total idiot and tries to suggest that the only person you've let down is actually yourself!