I'm going to paraphrase a bunch of things to make a point.
Someone asked how to develop mental toughness.  The answer is easy: Do things you don't like to do. Things that scare you or disgust you or chores that you dread.  At the same time, cut out things you do enjoy if they serve no purpose.  What have your hours or maybe years of TV watching done for your life?  No excuses.
That was my answer and the guy kind of chuckled and said, "No, seriously.  How do you develop mental toughness?"
Another wants to develop fighting skills without the ick factor of touching people.
Years ago (and the day I decided I really liked Steve Perry) we were on an Orycon panel on the future of pharmaceuticals (and I have NO IDEA how we wound up on that panel).  Steve asked the audience; "If there was a pill that would increase your energy, make you more attractive to members of the opposite sex, make you better at sex, make you live longer, lose weight and even make you smarter, would you take it?"
The audience clapped and smiled.
"Would you pay a hundred bucks a month for it?"
"Hell yeah!" the audience cheered.
"Well," said Steve, "It's called 'eat right and exercise' and I can tell just by looking that most of you aren't doing it."

People want things to be easy.  They want something for nothing.  I get that.  But there are some subjects where it is not possible.  Your body is not designed to improve under conditions of comfort.  It improves under stress.  With stress, muscles grow.  Without stress, muscles atrophy.  You don't get better at running by sitting.

You can get to a certain level of knowledge without pain or exhaustion.  You can get to a certain level of skill.  But you can't get good .  You can convince yourself you're good.  As long as you hang with other people who have avoided the same things you have, you can be comparatively good.  But you can't get good.  Not at fighting and not at competition level anything.

It's gonna hurt.  It has to.  People want a magical method where they can learn to deal with shock, surprise, pain and exhaustion without feeling shock, surprise, pain and exhaustion.  That's not the way the world works, kids.

And I'm not just talking about the swimming analogy-- you know, where you compare learning about any fighting system without fighting as learning to swim without water.  That's not what I'm talking about this time.

 You can't get good inside your comfort zone.  You want to get stronger?  Your muscles have to hurt.  Want to get flexible? Don't overdo it but you have to stretch beyond your comfort zone.  Want to get anaerobically endurant? You have to push until you are sucking wind.  Maybe puking.

Want to be better at a motion than the other guy?  Then you either practice more than him or more mindfully or, ideally, both.

In "Campfire Tales from Hell" Dan Gilardi did a little article called, "Want to Learn how to Win?  Learn How to Lose."  Essence is, unless you go into challenges that will kick your ass you will never rise to the level of skill or 'mental toughness' or conditioning required to meet that level of challenge.

When in doubt, push.

Some of our training-- with the team, with Dave, with Wolfgang-- literally scared people.  People would walk in and walk out after watching one class.  Administrators would say, "Is that really necessary?"  For their jobs the answer was "No." For our jobs, yeah, it was necessary. It never stops hurting, you just stop caring.  Some would tell us it was unnecessary.  A few openly called it abuse. (But these are the people that think that sore muscles are a punishment.)

I'm worried, frankly.  When people start having a knee-jerk reaction that pain is bad and discomfort is bad it seems like a short step before they start classifying Olympic level training (as an example) as child abuse or torture.

Caveat here, before I close:  Train hard, don't train stupid.  Injuries make you less survivable.  And there is no gain in emotionally abusing a student.  They have to feel emotionally safe in order to learn about physical danger.  For that matter, if you feel safe emotionally abusing your self-defense students, you aren't teaching them right.

That said, all valuable training happens outside the comfort zone.  Physically, mentally, emotionally you have to push the envelope.  It's gotta hurt.