Opening up is about being willing to engage with the experiences that are already there. It is about unhooking from challenging thoughts that jerk us around and about turning towards uncomfortable and painful emotions.
Unhooking
Unhooking (or defusion how ACT calls this skill) is about learning to put thoughts in a new context and engage with them more effectively.
Acceptance
Acceptance is about skills acknowledging, allowing, accommodating and appreciating our challenging and painful inner experiences.