Sometimes we know what God has called us to do and where we’re supposed to be, but we don’t always know how we’ll get there. Sometimes we get there even if we didn’t participate the way we were supposed to.
For an Old Testament example, Samson was supposed to deliver the Israelites from the Philistines. He did so, but because of the way he chose to participate (or not participate) in God’s plan, Samson had some really rough patches and ended up dead by the time it was done. (For more explanation, see Sovereignty of God and Volition of Man.)
For a New Testament example, Paul the apostle was called to stand before rulers to tell them the Gospel of Jesus. He participated exactly how he was supposed to, yet God’s will was for Paul to get there by being persecuted and arrested. (For more, see Paul’s Prison Ministry.)
God’s will isn’t always so extreme, but sometimes we forget that God doesn’t do plans like we do. He can plan seemingly unrelated things to tie together for His overarching plan.
A little more:
The Consequences of Doing God’s Will