You are taking a personality quiz online and face a question which asks you if you feel people don’t get your problems. You feel silly admitting (even to yourself) that that is true. But when you pop three painkillers in a day (with pure hatred for the concept of painkillers) and find no relief even for an hour, you do wish somebody understood your problem. Because clearly nobody does. And clearly your pain is unbearable.
Mental pain works the same way. The only difference is that the above is relatively more visible. That is all. And a lot of people do not seem to get it.