Think of how you can make a verbal conscious decision to learn how to ride a bike. Then you get on a bike, and you make a verbal conscious decision to keep your arms stable. Even though you made the choice, your arms won't obey you the first time. Because stabilizing limbs rides the line between a conscious and subconscious activity. But you keep making that choice, and eventually your arms obey you. With more practice, your arms obey a choice you haven't made verbally or consciously. You're riding a bike so of course you want your arms to be stable.

The meaning of choice is not just the single incident of a conscious verbal decision. There's a meta choice, where a choice is made many times over many attempts, until the associated action becomes subconscious. That's the only way we can choose to drive, read, speak, ride a bike, swim, and so on.

This extends to emotions. You only know you're angry after you've become angry. It feels like anger comes from somewhere outside of your control. Yet you can still choose to not be angry, even though you already failed. The more you choose not to be angry the less angry you would be.

It also extends to thoughts. Harmless intrusive thoughts, or distracting useless thoughts, or painful thoughts, all of these pop in without choice. You can still practice exerting choice over a subconscious process you can't control. Even though thoughts come from no where, people who meditate often (pretty quickly too in my own case) exert control over that subconscious area and stop thoughts from even happening.