"To eliminate the issue of reliance that easily, however, one would need to limit cognizable reliance to specific instances of sexual activity. But to do this would be simply to refuse to face the fact that for two decades of economic and social developments, people have organized intimate relationships and made choices that define their views of themselves and their places in society, in reliance on the availability of abortion in the event that contraception should fail. The ability of women to participate equally in the economic and social life of the Nation has been facilitated by their ability to control their reproductive lives. See, e.g., R. Petchesky, Abortion and Woman's Choice 109, 133, n. 7 (rev. ed. 1990). The Constitution serves human values, and while the effect of reliance on Roe cannot be exactly measured, neither can the certain cost of overruling Roe for people who have ordered their thinking and living around that case be dismissed."