If there's any doubt on either end, regarding the mental and the physical components of the climb, it will be shaky at best.
The clue (for me) that I've done due diligence with a particular climb is if I can, on the final go, just feel like I'm "walking up it" in a seemingly effortless manner. And I'll have the same psychological state of calmness and confidence from the bottom to the top. For me it's a really light and free feeling of having FUN and being able to do what I want.
Pay attention to Spider. Look at Largo and the pain, expenses, etc. he's going through after falling in a padded gym. Ask yourself if it's worth the price. And keep in mind all those bone-racking jolts from jumping off up high, even on mats, will pay negative dividends both anatomically and neurologically as you age.
You're right, it is always important to be forward thinking of the possible outcomes of something like this. The risks to the body long term have to always be taken into consideration even if you don't get hurt in the initial falls that are taken.
Highball bouldering is flat out STUPID and gaurenf*#kinteed to get you hurt. Either rope up or solo but don't think it's ok to fall just becuse there is a pad down there somewhere and that is how they do it in the magazines....
I think the knowing-in-your-bones "I can" is a product of putting in time doing the activity so there is a deep level of experience-based intuition to inform it, and the fitness associated with it. Time away from it dulls the fitness edge, and the mental edge, and the coordination/skills of operating at a high level of proficiency.
Having an injury fall is a big input factor for future fear calculations, understanding more precisely and deeply where our limits are and what are the consequences of failure. But when we digest that, our judgement of "is it worth it" will be more accurate than before.
Maybe the most important thing is to listen to our own assessment of "is it worth it" and be willing to walk away. If we're not ok with walking away from a challenge, we're not ready for it. There is too much emotional need clouding the rational calculations of risk.
Werner managed to say the same thing with one line.
I come from a gymnastics background and if you missed your mat while learning a trick it would be considered a major f**k up and your peers would think twice about your mental capacity. When learning hard tricks there is a long progression and you don't move on to the next progression until your totally ready , the big mistakes usually happen when you skip progressions. Glad you didn't get too hurt.