Hmmm. I don't know - the biggest challenges always feel like the biggest successes when you've overcome them. So I'd not take away any of the things I've actually learned.
But what I'd try and take away would be my odd obsessions with the unimportant things. Things like:
The amount of time I've wasted making Sublime Text look nice, or learning Vim, or playing around with every shell under the sun - without getting along with the actual coding bit. Ridiculous.
So, yeah - that's what I'd ask/help beginners with. Please stop adding to your problems with incidental crap and just use the quickest, most basic set up you're comfortable with.
We're a place where coders share, stay up-to-date and grow their careers.
We strive for transparency and don't collect excess data.