Did my 20 today. I actually got a 2000+ rated tactic! I'm still in the low 1800's.
I studied game 10. It was short and there wasn't a whole lot of content to the game. What I learned from the game can be summed up in one graphic (see below). I think Chernev's point of this game was "It is important to dispute control of the centre."
By not disputing control of the center, White was able to attack h7 after Black castled. White's knights also were well placed. Black had to disrupt his castled pawn formation. White was then able to decisively move in for the mate. Had Black disputed the center, he would have been able to defend the castled king and have a more open position with more options on the table.
I went over game 11 too today. This game reinforced previous ideas. The best thing I learned from this chapter was why we are to defend the center of the board. In all honesty, I've heard this advice many, many times, but have not heard many reason as to why. Chernev said,
"Anchor at least one pawn in the centre and give it solid support. Pawns in the centre keep enemy pieces from settling themselves on the best quares."
If we guard the center, our opponent cannot get a foothold with which to launch attacks on our king. If we control the center, we can launch our own attacks into enemy territory.
That is all for today.