Just adding my 2 cents (dollars or euros, whichever you prefer) concerning one specific aspect of DIY that I found out from experience (it has been hinted in a previous post): pride!
I've not had a technical training at all (I'm a DPsy), but I started putting ikea furniture together some 17 years ago (preparing for the arrival of my oldest

) and simply applied the pragmatic approach: buying at ikea simply meant that you would
have to put it together yourself. So even though I screwed up a thing or two, in the end it would work out.
After I divorced and remarried my inlaws turned out to be a family where DIY was much more common, not so much because of their background (my father-in-law is a teacher and my mother-in-law a psy nurse) but their spirit was much more creative (my wife is an art director) and building things was something they took (and take) great pleasure in. I found that they managed to awake that spirit in me as well, and when the occasion occurred (my son was moving to the attic, which was just that: an attic with just the washer/dryer and nothing else) I offered to build him an appartment. It took me several weeks, but I learned to build walls, lay floors, basic wiring... my son was very pleased with the result and that made me feel very good about myself.
And then when we bought our current home/building site, where
everything had to be redone, and money was not available in abundance after we bought the complex (mind you, no mortgage) I decided to go all the way and do most of the work myself. This meant not just basic DIY, but a complete overhaul of an entire two-story building, including replacing all wiring and electric installation, plumbing, heating, floors, ceilings... it's been two years and it's far from finished (I need to work from time to time

) but every effort, every drop of perspiration (and blood, that happens too) has had an immediate and lasting result, which is exactly why we engaged in this adventure in the first place. We bought the complex to be (or become)
our corner of the world, and I've poured my soul into it (and lots of ikea furniture). I've made mistakes, I've gone over my head sometimes, and sometimes I sat and wondered why I'd gotten myself into it and how I would ever get the job done, but in the end (or up until now) it's all been worth it. For me, that's exactly what DIY is about; not so much saving money, doing it sooner or faster, but doing it
myself. Making this house a better place is making a small part of the world a better place and making me a better person.