How can I be sure of the right motive, when trying to please God?

To this we might simply reply, “Are you trying to please God?”Then that is the right motive!

Do not try to overcome sin because of the shame you feel, because of what others think or say about you, or because you want to feel better. Seek to overcome sin so that you may walk in closer harmony and fellowship with Jesus.

It's all about Jesus. And Jesus says, "If you love me, keep my commandments."

Pleasing God is not about feelings, or intuitions: it is a matter of reflecting his perfect will, expressed to us in his Word the Bible, so that he is pleased by what he sees in our heart, our thoughts, and our actions.