This recovery is slower than we would like it to be and more frustrating than it ought to be---but when we consider what was surgically done to the knee---the cutting, the sawing, the pounding, the gluing, etc---it all does finally make sense.
Recovery is like a roller coaster ride and you will have some good days and, for no apparent reason, some real stinkers, too.
Do not let those other people get you down---they have not been where you are and do not understand how tough it is to go through recovery! We do, and we will be here for you!
Just take it one day at a time, and do not worry about---you will reach your destination! My own recovery from a BTKR took five months to lose a pesky limp and it was not until about eight months when I was feeling "pretty good"!
I, too, was fed up many times during my recovery, and I kept asking my PT's "WHEN"? They would simply smile and say, "You will get there, but your knees are in charge." You will reach your destination and you will be fully recovered----and you will feel great! Down the road, these frustrating times wil melt away or become memories of your struggles in your victory!