What triggered this increase is realising the difference of value in stones. Some stones have served their purpose after they are played (e.g. most kikashi), some stones just mark the boundaries of territorries (if not important for group stability these can be treated lightly) while other stones are essential and will be fought over (cutting stones, heavy groups). This made me tenuki more and evaluate sequences I would not have seen before (walling off a section by sacrificing for example).
Another reason for the increase is playing games with more time (30 min main time), because I lost on time a lot before.
Is it usual to experience this sudden increase strength? And if I win almost all of my games at 9kyu, what could be my real strength?
I am asking because it's more fun to play even games than to win every time.
Furthermore, I am interested in your winstreaks and how you felt about them!