Justin Taylor’s gentle, respectful response to John Piper notes this:

(1) The fact that God ordains all things (i.e., his secret will) has a limited effect on our decision making. It can’t prescribe how we act, but it can prevent us from having the wrong perspective (e.g., anxiety, fear, despair, misplaced trust, etc.). But in terms of interpreting events, the main way to read providence is backwards (as John Flavel wrote: “Some providences, like Hebrew letters, must be read backward”).

(2) The fact that God ordains means ensures that our actions have significance. The ordained outcome can never be seen as an excuse for complacency or fatalism.

Calvinists believe in God-ordained means. This is not merely a platitude. John M. Frame says it well in Apologetics to the Glory of God: An Introduction (Phillipsburg: P&R Publishing, 1994):

The relation of divine sovereignty to human responsibility is one of the great mysteries of the Christian faith. It is plain from Scripture in any case that both are real and that both are important. Calvinistic theology is known for its emphasis on divine sovereignty—for its view that God “works out everything in conformity with the purpose of his will” (Eph. 1:11). But in Calvinism there is at least an equal emphasis upon human responsibility.

An equal emphasis? Many would not be willing to say that about Calvinism. . . . God’s sovereignty does not exclude, but engages, human responsibility. Indeed, it is God’s sovereignty that grants human responsibility, that gives freedom and significance to human choices and actions, that ordains an important human role within God’s plan for history (pp. 14-15, emphasis added).