We have recently started building an aquaponics system. There is nothing like a new project to start the mental juices flowing. We're learning about water quality, raising fish, maintaining nutrient levels for plants... you name it, the list goes on. Fortunately, we found a great resource in the aquaponics forum at Backyard Aquaponics. The people there are great at providing whatever knowledge they have. They are excited about aquaponics and the ability of individuals to grow their own fish, vegetables and even some fruit in an easy setup in their own backyards.
I could read for weeks on the forum and not cover everything. After a while, my mind becomes mush and I have to walk away. But the fact is, my mind is working overtime to understand as much as possible so we can start off on the right foot with the system.
If you're bored with life or you just need something to get you excited again, choose something new to learn about. I've heard in the past that keeping the mind active is important as we age. I remember the story of a great-aunt who was in her late nineties and "sharp as a tack". Her secret was to keep learning, and to spend time each day in some mental activity. I know I'd like to be in my nineties and still learning... keeps life exciting. So, go learn something new!