I had the exact same problem when I started! I think I played one game, then two simultaneously, which was an enormous time/energy suck, then said, "Never again! One at a time from now on."
Of course, I've been able to handle a couple simultaneous games more recently, but only when I don't have too much going on, and only because I finally have enough experience that I can recognize cards by name, maybe with just a glance at the codexcarddb.com image, and I'm finally mostly comfortable with the spreadsheet.
Even with the experience, some of the really tense games, esp. once you hit 8+workers, can be mentally exhausting. Thrilling, but tiring at the same time.
I find it helps to remember that asynchronicity is a blessing: as with texts on your phone, just because many people respond right away doesn't mean you have to. In our game, you should feel free to take a day or two (or five!) off if that's what you need for real life or to finish another game. I guarantee I won't be offended. (Occasionally I and others will give a nudge if a game's gone several days/weeks w/o response, but that's more for tournament games w/ a time limit, or to make sure the other player is okay and/or hasn't forgotten about it. Everyone here understands that real life takes precedence, in my experience.)
The thoughts section is great for spectators, but it's also great for letting you pick a game back up after days away and still have access to your old plans. (: