Sometimes the best way to become something you aren't, is to pretend that you are.
If you want to be more assertive or kind or empathetic or a better listener, pretend that you are those things until those things become more true.
Try it with your physical body first. Let's fake depressed feelings - slink down in your chair, lower your shoulders, lower your chin, and relax all of your facial muscles. Sit like that for 10 seconds and what do you feel? Happy, pumped, excited? No. You probably feel down and disappointed. Your mind has the same power to change your behaviors by contriving the context.
I'm not suggesting you be disingenuous. I'm suggesting you simulate who you want to be out of an earnest desire to be better.