It's one of our most irritating comments we come across, notably those without any mind struggles tell us basically that we have the choice to overcome our symptoms with mind control in a split second "snap" and we'll be normal.
Of course, someone that has the normal capability of mind control would wonder why you can't do what they do. Not only is that lack of empathy (also a serious deficiency of the mind) but it is simply naive.
Like all matters however, why dont we remove the anger and emotions about this and examine if there is an elememt of truth to it, I think there might be.
i think it lies in enambling those with a MI. As a child have you ever about to cry and your mother points at you and says "stop" or some other direction that causes you to stop your path towards crying? You stop and hold it in why?- because you you were told to by someone in authority in a direct manner.
Dissecting this a little. If emotions at that moment were uncontrollable you would still cry regardless right? Does this mean you wanted to cry as a choice? And your mother countered that choice.
If you had soft parents that , everytime you cried you got sympathy, would you allow yourself to cry more ofyen? Of course.
As adults when we have depression or other struggles we no longer have that parent telling us to, get out of bed, go to work, stop crying... Does that mean as adults we dont need that? We do often need such prompts because normally it should come from ourselves...but alas, we haven't got it in us...the person saying "snap out of it" does! We didnt develop that control or we lost it.
So, imo there is an element of truth to that direction only in that such directions are absent from our own capability.
Being told to "snap out of it" can be used as a reminder of how our mood is effecting our behaviour and how frustrated others can be about us. We can answer them like this
"have you known anyone that has "snapped" out of it?"
"Is "snapping out of it" a proven psychiatric process, a reflection of your qualifications maybe?
But you are far better off putting such directions aside as naive and ineffectual. If however you take the direction and turn it into a motivating tool you could use it as an example of what you lack- the minds isolation to some abilities lacking and work on them via therapy and recovery.
"Snapping out of it" is needed by professionals over a long period of therapy not by people clicking fingers.