My family gets on my case all the time regarding my OCD, like I do this on purpose just to piss them off, so in my frustration I tried coming up with someway to make them understand what it's like living with mental illness like OCD or other anxiety disorders. Here's how I experience it:

Imagine you're sitting in a chair in the middle of a room. The state or appearance of the room doesn't matter. except that there are two buttons in front of you: one red, one blue. You are then told to not think about the red button at all. Sounds simple, right?

Wrong, because trying not to think about something makes you think about it even more. So you distract yourself with whatever you can to prevent yourself from thinking about the red button. To complicate matters however, at random intervals someone will pop in to remind you to not think about the red button. Every time you do think about the red button or so much as glance at the red button, speakers in your chair will blast out loud, obnoxious noise, increasing in volume every 30 seconds. Should this happen, then there are three ways to stop it.

1) Hit the blue button
2) Hit the red button, but something bad will happen
3) Wait ten minutes for the noise to stop

Inevitably, you end up thinking about the red button and sooner or later pushing the blue button. You then go on with your life until you end up thinking about the button again and once more hitting the blue button. Sure, sometimes you might try to outlast the music, but in the end you'll break and hit the blue button. You might even try to hit the red button once or twice, but the ensuing consequences will make you afraid to do so ever again.

Eventually, it will get to the point that the second the idea of the red button enters your head, you're already instinctively hitting the blue button, maybe even just randomly hitting the button just to be sure. You know it's stupid, that there's no reason to do so, it takes up untold amounts of your time to the point it might be all you think about and you know that there are better ways to stop this, but you can't stop yourself lest you suffer the loud noise.