Good days bad days

There was a time period, about a year and a half ago, when Genna was going through her terrible twos & threes. So many things were a struggle to do with her. During that same period, for the most part, Jonah seemed to be angel. He was so happy, agreeable and easy. Over the course of the past year or so, this seems to have switched. Jonah is now going through his terrible twos. He's refusing to nap, needs to nap, then gets so exhausted that he's in a miserable mood in the evenings (and often at several points during the day). Genna, on the other hand, is now my dream-girl. For the most part, she is sweet, agreeable, independent, and occasionally a little helpful. Today, after school, we went to the beach. Genna packed a bag for herself that included a water bottle, a blanket, colored pencils and a coloring book. When we got to the beach, Genna unfolded her blanket, spread it out, opened her coloring book and then proceeded to color on the beach for an hour. A few times, she looked up to see Jonah and I, then she talked to a couple of girls (probably about 6-months younger then Genna), then she filled her water bottle with sand. During this same time, I was running around the beach chasing Jonah and constantly telling him to not run away, to not throw the sand, to stop playing in the fire rings, and to don't go in the water unless he's holding my hand. This was a particularly difficult afternoon with Jonah. However, occasionally, Genna has a bad day and requires extra attention. Strangely, on these days, Jonah is quite good. It is almost as if the kids secretly plot about who's turn it is to have a bad day. It's very, very rare when both kids have bad days. Somehow they seem to know that mommy & daddy can only absorb so much whining and then they respect that threshold... usually.