I definitely had to experiment as well - I bounced around between Claritin and Allegra for a couple of years. I did try Zyrtec and experienced significant fatigue with it, which led me to stop using it pretty quickly.

Earlier this year I discovered Xyzal (expensive, but does have generic versions, too), which appears to be a close relative to Zyrtec. Interestingly though, they recommend taking it at bedtime rather that in the morning, the idea being you'll get a better night's sleep from not being congested AND you'll sleep through the worst part of the fatigue from it. This has worked out well for me - my allergies have bothered me less this year than they have in the last ten years or so, and I sleep better at night (I've had problems with insomnia off and on for ~20 years).

RE: the OP, I'm in my mid 40s and have always had some issues with following through and not procrastinating, and my sister was recently diagnosed with ADHD, so it's probably something I should at least discuss with my doctor at my next physical.