I believe the saying you are referring to is "What you stand for ..."
If you "stand for" something, you believe in it, or strive for it.
A concrete example of this can be seen in most national parliaments in democracies. If you sit on one side (all members of the same party sit on the same side of the chamber), then you "stand for" big government, big taxes, social welfare, socialism.... If you sit on the other side, you stand for small government, private enterprise, capitalism, etc.
If you sit on the fence, you stand for nothing.