The whole of Romans 8 talks about the choice we have to make. A choice between flesh and spirit. We stand in the gap, being pulled toward both forces. We are the referee who decides the winner of this cosmic battle within our soul.
One of the hard things about choosing the spirit is trusting in God. So much of what He asks of us is counter-intuitive: lose our life to find it, rejoice in suffering, etc. His commands start to sound burdensome to us. We start to think we should just be able to do it our own way.
In verse 15, Paul counters this perspective with the truth. God is not a task-master; He is our father. Choosing the way of the spirit puts shackles on our flesh. It dims the parts of us that are not compatible with the Kingdom of God. If we are not careful, we start to feel as though that is a problem. But God knows what is best for us. He calls us, not as an oppressor, but as a Father. He wants what is best for us.
God is not about rules for the sake of making you follow rules. He is about enhancing our freedom through a proper understanding of boundaries and consequences.
Our choice is about trusting our Father to have our best interest in mind. It is about submitting to His authority and uniting to His purpose. The flesh looks to bind us. The spirit looks to set us free.