If a bad thought is persevering in your mind, continuing in your mind, then it means that you are just calling it a bad thought. Deeply you are supporting it; deeply you think that it is a good thought. We call them bad. We actually do not consider them bad.
And your mind is not at all full of ‘good thoughts’. What does that mean? You call them good, but you consider them very, very bad. So, even when those thoughts come to you, you do not support them. What do you support? All the so-called bad thoughts, because they are all quite nice, lovely, and attractive.
Let’s have a little honesty, then. Why call them bad at all?