"Let your 'Yes' be 'Yes,' and your 'No,' 'No'."1
I'm sure you know some people who won't take no for an answer. They're boundary busters who have no respect for other people's personhood.
Healthy boundaries are to protect ourselves from toxic people, from controlling and manipulating people, from con artists, from abusive people, from people who can hurt or use us for their own ends, and so on.
External boundaries are needed to protect our physical well-being. Nobody has a right to come into our space, get into our face, or touch us without our permission.
Internal boundaries are to protect our feelings. Nobody can upset us, hurt our feelings, make us feel guilty, ashamed, afraid, or angry without our permission. This is why we need good internal boundaries.
Boundaries are not walls. Boundaries allow the people in that we want close to us. Walls shut everybody out. Boundaries are also needed to contain our own "badness" so we don't hurt others.
Without healthy boundaries, people will walk over us, use us, or abuse us and we will end up feeling angry, upset, hurt, and maybe even wallow in self-pity. What other people do is their responsibility. What we allow them to do to us is our responsibility. This is why we need healthy boundaries without which it is impossible to recover, grow, and live meaningfully.
Furthermore, without the freedom to say no our yeses are meaningless.
Read the life of Jesus in the gospels for a good example of healthy boundaries. Nobody ever controlled, manipulated, or did anything to Jesus without his permission—including his parents once he became a young man.
Suggested prayer: "Dear God, please help me to develop healthy boundaries to protect others from my 'badness' and to protect myself from others' 'badness.' And help me always to respect other people's boundaries. Thank You for hearing and answering my prayer. Gratefully, in Jesus's name, amen."
1. Matthew 5:37 (NIV).