This is one of "22 virus definitions" (thought-mistakes that cause ineffectiveness and unnecessary negative emotions).
If you are making this mistake in any of these ways, you're probably proud of yourself for it. That will make it harder to admit the thought is a mistake. But go through the process of writing down your thoughts when you are demoralized or upset, and misplacing responsibility is bound to show up as a mistake.
In the antivirus for your mind, we're not trying to be positive. We're trying to be accurate. So if you find you have a thought like, "It's all my fault," you have to really look at that. If it really IS all your fault, you have not made a mistake. But if you look at it honestly and realize it isn't entirely your fault, your distress will fade right on the spot.
See the complete list of definitions: The 22 Virus Definitions.