Not falling back into our old selves is a fear I deal with as well. Finding that balance between the old pieces I adored and the new pieces I have worked so hard for is what I am striving for right now.
When I have particularly stressful or comfortable situations especially with H, I find myself more old Ruby sometimes. But at least I am aware and try to make that shift.
Do you find you are scared that if she was back in your life, so would all the old behaviours? This is just a question btw, not an insightful probe lol!