The 'State Action' Conundrum: Lochner v New York & Griswold v Connecticut

Yaar samajh nahi aaya... I'm getting all confused with the concepts of 'state action' and 'economic substantive due process'. In Lochner v New York (1905), the court found that a New York state law regulating working hours was unconstitutional because it interfered with the 'liberty of contract' between employer and employee. But then Griswold v Connecticut (1965) comes along and applies the same liberty of contract idea, but this time to strike down a state law prohibiting married couples from using birth control contraceptives. How can the same principle be used to attack a law that regulates the market economy (Lochner) and at the same time be used to protect individual autonomy (Griswold)? Please help, I'm all lost!