Here are a few other quotes which helped me to find peace with this question:

The above from Miscellany, page 233, has this as the very next sentence:
Ignorance of self is the most stubborn belief to overcome, for apathy, dishonesty, sin, follow in its train.

“The Ego”, from Unity of Good, by Mary Baker Eddy, page 27:
…we shall find that evil is egotistic, — boastful, but fleeing like a shadow at daybreak; while God is egoistic, knowing only His own all-presence, all-knowledge, all-power.

Parthens’ Forum Post from February 21st, 2019 on the subtraction of self.

From Mary Baker Eddy, Her Spiritual Precepts by Gilbert Carpenter:
Once Mrs. Eddy told Laura Sargent and Clara Shannon, that she thought she had discovered the way to eternal Life, and that was, whenever she wanted to do something for herself, to put self aside, and do something for others; just to learn to be unselfed.

From page 304 of Addresses by Martha Wilcox:
Within our individual self is the battlefield, and there, too, is found the victory. We need to watch our thought that it does not become confused with the issues of the day. We need to be spiritually keen and alert in our thinking. We need to be “undisturbed amid the jarring testimony of the material senses” and prove that “Science (is) still enthroned.” (S&H 306:25, 26)

Finally, Mrs. Eddy’s words from page 77 of Collectanea:
If you but knew the infinite capacities of your being, the sublimity of your hope, the grandeur of your outlook, you would let error kill itself. It comes to you to give it life and you give it all the life it has.