First of all, I am kind of crazy and I just love to mine. There's something about it that is nice and calming.
However, mining in the Ruby Sea is especially calming. Nice underwater, no enemies to be had and the background music is great. Couple that with a good movie (or my personal recommendation: Bob's Burgers) and you have a recipe for success!
The positives from this is the millions of gil you make.
So, if leveling or dungeon crawling has you frazzled, pick up a pick and go to town!