Last night, I played a blitz game that illustrates this problem with blitz. In contrast to calculating the consequences of a rook exchange and then playing the pawn ending correctly, I intuitively guessed that I would benefit from an exchange of rooks and then threw away the pawn ending.
Black to move
32...Re3+ was the correct move. But then, 33.Kd4 Rxa3 34.bxa3, it was time to assess the resulting pawn position.
I played 34...f5, playing hope chess. I hoped that my opponent would facilitate my dreams of a passed pawn with 35.gxf5. He refused to cooperate, playing instead 35.a4.
Did I then seriously consider 35...e5+, a move that may at least hold the draw?
No. I played 35...fxg4 and quickly reached a position that was hopelessly lost. Several moves later, we reached the position below.
White to move
My opponent wins easily with 44.Kf5. However, 44.Kd4 was played. In the ensuing pawn race, we both promoted pawns. The queen ending was a dead draw. But, as often happens in blitz, a series of senseless checks were employed to run the other player out of time.