Space

In general, if an opponent has more space, you should trade some pieces off (giving you more room to move about in), create your own spatial plus in another sector of the board, or use pawns to break open lines so your pieces can penetrate, or weak squares or pawns are created.The one thing you should NOT do is dither about and moves your pieces aimlessly here and there until, to your horror, you realize your completely bound up and helpless