Do I really have to go along with the plans we made?  I'm going them turn down.
Why would you want to turn those plans down?
I'm going to be selfish and think about my needs for once.
I hear you, but it is wrong to turn down plans that you already agreed to. They involve other people and they will be affected by your choices. You should have thought about it before you made the committment.
So what? I'm going to do it anyways.
You need to understand the inconvenience you're causing to other people. If you broke your promise once, nobody will ever trust you. I suggest you to fulfill your commitments this time even though you don't want to.