This is a popular verse these days. You see it on coffee mugs and key chains everywhere you turn. But as often happens with verses that become trendy, they are often used out of context. Some seem to mean with the verse that it’s all good, that as Christians everything should be constantly going our way. After all God wouldn't have a bad plan for you, would he?
The context of Jeremiah is not a happy one. Jeremiah Is often referred to as the "Weeping Prophet' for his message was particularly difficult. He prophesied to the last days of the kingdom of Judah and into its fall. He may have been taken to Egypt in exile, where popular theory says he died a martyr’s death.
Yet always in the gloom and doom of a prophet's message God would point to a time of restoration. Chapter 29 points to such a time, a time of return and promise, but also a time of repentance on the part of Israel. God's plan for them Included this time of exile, but he also knew that through this they would learn to look to him again, and trust him. When they were ready God would also restore his blessings and promises to them.
Jeremiah 29:11 isn't about God approving our plans or even making life easy. It is about God being faithful to his purpose and plan. When we learn to trust God's plan and to follow him, then yes, those plans will prosper us and lead to a hope and a future.