While it is certainly true that tit-for-tat exchange of this sort can help create an ongoing, mutually supportive relationship, it has only really done so when it stops being strictly tit for tat. Graeber, Toward an Anthropological Theory of Value, p.219

Sahlins, on the other hand, defines “generalized reciprocity” as the kind of open-ended responsibility that prevails among close kin, all of whom will do whatever they can to help the other, not because they expect repayment, but simply because they know that in a similar crisis, the other would do the same. He contrasts it with the “balanced reciprocity” that prevails between people who, though less close, are nonetheless close enough that they feel obliged to deal with each other on a moral basis. “Balanced reciprocity,” in- terestingly enough, would thus include both classical gift exchange and the less cutthroat forms of trade or barter. […] Rather than “generalized” or “balanced” reciprocity, then, it might be better to think of reciprocity as relatively “open” and “closed”: open reciprocity keeps no accounts, because it implies a relation of permanent mutual commitment; it becomes closed reciprocity when a balancing of accounts closes the relationship off, or at least maintains the constant possibility of doing so. Phrasing it this way also makes it easier to see the relation as a matter of degree and not of kind: closed relations can become more open, open ones more closed. It seems difficult to avoid the impression, then, that the closed reciprocity of gift and countergift is in fact the form of gift exchange that least embodies what makes a “gift economy” different from one dominated by market exchange. It is competitive, individualistic, and can easily slip into something resembling barter. Graeber, Toward an Anthropological Theory of Value, p.218-220