You may have heard someone say in passing, "Ugh! I am so OCD, this desk is a mess!" Meanwhile, you follow strict routines and take unnecessary precautions to things.
You may have heard a friend say, "I failed that test, I'm so depressed." Meanwhile, it is the first day you've gotten out of bed, the first day you've showered since the dark cloud cast over you and wouldn't go away.
You may have heard, "I literally can't. I'm like, having a panic attack!" Meanwhile, you did just have one, and you hyperventilated and shook for 10 minutes.
Or you may have even heard, "That song gives me PTSD, it reminds me of my boyfriend." Meanwhile, you still have nightmares or flashbacks about the traumatic event you've experienced.
This is not to say that people's mental illnesses don't all look different for the individual. You don't know their story or what they went through. This is for those that use a mental illness nonchalantly, incorrectly, or self-diagnose themselves with said mental illness without the advice of a trained professional.
By doing this, you are not only affecting your own mental health, but also the stigma around whatever self-proclaimed illness you have.
When you self-diagnose, you are adhering not to the actual symptoms someone who has that mental illness has, but to the stereotypes you believe go with that mental illness. You pretend to exhibit those symptoms and though you may not have that mental illness, you trick your brain into truly believing you do in some way. If you try and show everyone that you have depression to make a point, your behavior may lead to you actually becoming fatigued and depressed, and you will no longer have control over it.
It also puts a false face to the actual mental illness. By exhibiting false symptoms or stereotypical symptoms, it makes those who don't have that illness or already believe the stigma, it gives them the excuse to continue that stigma.
If you do believe you have a mental illness, or you believe you may need to seek help, please see a professional therapist.