Probably part of the reason why Jeremiah's ministry would be so difficult is that God wanted him to preach messages that would "tear down and break apart" people's favored ways of living that were contrary to God's plan. This would include holding onto age-old traditions that were more important to men and women rather than obeying God's clear instructions and commands. But God knew and He was teaching Jeremiah that some things have to be broken down before something new can be built. You see this in remodeling all the time. To put up new cabinets in the kitchen, for instance, requires ripping the old cabinets off the walls first. There's a lot of mess and things don't look so great! But when the new cabinets are installed then everyone realizes the destruction was worth it in order to see something much better.
Many times in Scripture God speaks of "being broken" as a good thing. Note Psalm 51:17 NKJV - "The sacrifices of God are a broken spirit, a broken and a contrite heart--These, O God, You will not despise." And in order for some hearts to be broken the preaching of God's word has to be pointed at dealing with sin. People need to feel conviction before they can enjoy forgiveness. Pain in the heart that causes someone to get back on the right path with God is worth it all!
The "building and the planting" gives the message of HOPE! God doesn't just tear down that which is bad and leave it a mess. God is constantly in the ministry of rebuilding and renewing. And that is an exciting part of our ministries! As I've said since the beginning of this year: Everyday can be a New Beginning!