Particularly in small teams, or just as an individual, there are so many factors which influence your working week. You can make a single small improvement—and it might be exactly the right thing to be doing—and then some unexpected external factor comes along that has other negative consequences. Even if you made a potentially very productive improvement the overall result is that you had a worse week than the one before.
It’s important not to miss the wood for the trees. Improvement is a long game. Any public stock that’s improved over a period of months or years still had days when the price ended down. Sometimes that lasted for several days. Any sports team that improves tends to do so over several seasons—they can still lose individual games here and there.
The important things are to (i) keep at it, and (ii) step back and take the long view. Examining just the minutiae is not productive.