In what ways have you sacrificed your self-respect in favor of validation from others? What have the results in your life been?
Seeking approval from other people can quietly cost you your own good opinion of yourself, and the quote asks you to count that cost honestly. Each time you stay silent about something you believe, laugh at a joke you find unkind, or take a path because it will impress others, you gain a little acceptance and lose a little self-trust. The second sentence asks you to look at the long-term consequences: the career you drifted into, the friendships built on pretending, the persistent feeling of being a stranger in your own life.
The question fits Mark Manson's wider view, especially in The Subtle Art of Not Giving a F\*ck, that we cannot avoid caring about things, so the real task is choosing what to care about and why. Approval from others is a poor thing to build a life on because it is unstable and out of your control. The idea also echoes older Stoic thinking, such as Epictetus's advice to focus on what is within your power rather than on others' opinions.
In practice, imagine someone who always agrees in meetings to avoid friction, then resents their workload and ideas. They might start by writing down three moments from the past month when they said yes but meant no, then practice politely voicing one real opinion this week and see what actually happens.