This is going to sound silly perhaps - but "relax" and change your focus. Example....i never have had trouble with bias edged blocks because i don't believe in bias edges.....they do not exist in my universe....and so i don't have any trouble with them. If you focus on the "problem" of your pieces not fitting - you tend to be more tense and "get" what you focus on. I'm not trying to be a wise gal here.....it's just a thought....
Alternating the direction of your seams when pressing to the side helps because you can "nest" the seams.
Also....i have more than once used the trick of a dot of Elmer's wash out school glue at important or difficult seam intersections.....it really helps keep those points/corners where they belong.