Hmm... I have officially been diagnosed with several mental disorders, and suffer a lot of problems leading a 'normal' life due to some other things which are incredibly difficult to define accurately (and thus diagnose.)
I sometimes feel bad about this, and sometimes feel I should just be able to 'get over it'... But irrational fears related to social situations can really cripple your life. No matter how silly they seem from a purely rational perspective.
I've had depression on and off too. And it's scary feeling like nothing is worth doing... Or worse yet, that being alive isn't worth it... I would consider I've never had anything worse than mild depression in my life, but I've still come close to trying to kill myself a few times...
And then there's something else too, which is technically listed as a mental illness, although I don't feel like discussing that right now...
So... Unless you've had to deal with it yourself, I would not think you can really know what it's like.
The main difference between mental and physical illness is that you can't easily 'see' mental illness.
Telling someone with a genuine mental illness they're just 'faking' it, and that they should toughen up and stop being so pathetic, (especially likely if you tell someone you have any kind of social phobia) is all well and good,
But it's basically like telling someone with a broken arm to go and lift weights, and stop being so pathetic. You can lift it if you really want to, you're just not trying hard enough.
I mean, no-one would do that if you've got a broken arm, and yet it happens with mental illness...
It's hard to get meaningful help for some problems too. I wish I could just 'get over it' and pretend like my problems don't exist, and thus do some things most people take for granted, but I can't. I've tried.
And the guilt of feeling as if you're not contributing to society because of some 'pathetic' problem that you're surely just making up is not fun either.
I mean, if you're intelligent, can hold a reasonable conversation with another person, and seem phyisically healthy, nothing could possibly be wrong with you right?
... If only...