"I know how you feel."
Many people say this to show empathy and support to someone who is going through a difficult time. This sentence has bothered me for years because it oversimplifies a person's experience and is often an inappropriate thing to say.
Experience is very complex. It is unique to every person. Going through something like a death, illness or financial issue does not mean you can fully identify with someone else who is going through or has gone through those things.
Any experience is based on many factors like your emotional state, your background, your support system, your socio-economic status and much more. It isn't really measurable. You can't quantify it with a number and any number would not help someone understand either.
You can't determine the severity or type of experience and compare that to your own. Experience is also subjective and perceptive. One person's perception of severe may be another's version of mild. This is all dependent on the unique, unmeasurable factors I described earlier.
I do understand why people are so ready to claim "knowing" your experience. Recognizing a shared experience is powerful. It can make you feel less alone and can motivate movements to change things. That's great. But to be truly supportive, we must also acknowledge our differences. Otherwise, especially if the empathy is incorrect and someone really doesn't "get it" or if that person's experience is completely different, claiming to "know" is offensive and ignorant and can actually make the person feel even more alone.