A nice week last week - I finished off the level 20s. Also, I went back over the ones I got wrong using the 'erroneous' filter and redid them until I got them all right. I tried this approach with the 10s and it works well. You get to repeat all the ones you didn't get the first time round ... or in some cases the second or the third time round!
My new plan is to progress this each circle - on circle 2 I repeated level 10 until I got them right. Circle 3 will repeat levels 10 and 20. And so on. Also, I'll progress the maximum level I try, so I stopped at level 40 on circle 2 and I'll aim to stop at level 50 on circle 3. At least that's the new plan this week. I'll see how I get on with this as this circles progress.
It is an interesting exercise to repeat the problems you got wrong - it highlights areas of weakness in your thinking. I think mine fall into two areas:
(1) blindness to certain themes
(2) not enough breadth of analysis.
(1) blindness is easy to spot. Here's a good example (problem #149):
I thought through the problem to this stage (problem #149 a couple of moves later):
But then thought, "So what?". I couldn't see that taking either rook would open up the back rank mate.
This is an example of (2) - not enough breadth of analysis (problem #259):
I kept wanting to play h4 instead of f4. I am not thinking through all the options thoroughly. In fact the only way I managed to finally solve this problem was by learning f4. Am I just learning some of the specific problems off by heart rather than understanding them? Is this bad? Or will I remember the pattern somehow?
There are other examples where I get carried away with quite a complicated line of analysis, only for it to not draw any definite conclusions. My initial thought is that I'm just not seeing deep enough, and there is in fact a solution possibly a couple of moves more ahead. What I'm really doing though is missing an easy 2 or 3 move combination! I can get distracted focusing just on one line and miss a number of other (simpler) ones.