How do you know you’re ready to change the thought?

Hi Brooke,
On a recent call, you said that we need to fully understand our thoughts and the feelings they cause first before we can think about changing our thoughts. We have to be present with the pain first. We shouldn’t rush to change the thought. That makes sense to me, but what I’m wondering is how do you know when you are ready to change it? How do I know that I am present enough?