Expectations from a Relationship

Any relationship revolves around a mutual give and take. At times we give more and take less, and vice versa. Each relationship has an equation of giving and receiving, which is unique to it.
From the inception of a relation, slowly, but surely, a pattern emerges, as to how much, each partner is contributing to the growth of the relation, and how much he/she is expecting from it.
So each partner is responsible for etching a limit of expectation in the other's mind by establishing a ritual, a habit of giving a particular thing, perhaps at a particular time.
What happens then, when without asking or informing, any one of the partner withdraws from that pattern? Shock, suffering, pain and hurt surfaces in the mind of the other partner.
The solution perhaps is to not expect anything from anyone. That however, is a hypothetical solution. It is not humanely possible.
Perhaps an attempt at keeping the expectation at a minimal level, consciously, from the start, is a more feasible solution. But, again what is the benchmark of that level?