Why does setting a boundary make us squirm?
Because we make too big of a deal out of it, that’s why!
Boundaries are nothing more than an invisible barrier that determines where we end, and the other person begins. They define our identity. They tell others what we believe, what we need, and how we feel. 
Setting boundaries can be stressful; I will give you that. However, that stress does not last long. It is sort of like ripping the adhesive tape off your leg. The faster you do it, the less it hurts.
However, we worry about upsetting someone or fear a potential backlash of anger. We fail to protect our sacred space because of our desires to please or accommodate someone. Yep, most of us would rather be miserable than say “No” to someone.
Without boundaries we find ourselves giving out of compulsion or obligation, rather than love. We feel pressured, rather than blessed and resentment starts to build. People with healthy boundaries are more caring and compassionate because those boundaries help them stay out of resentment with people they are willing to help. They do not try to rescue anyone, and instead of solving a problem for someone, they solve the problem with them.
Even Jesus had expectations for people in need.
One who was there had been an invalid for thirty-eight years. When Jesus saw him lying there and learned that he had been in this condition for a long time, he asked him, “Do you want to get well?”
“Sir,” the invalid replied, “I have no one to help me into the pool when the water is stirred. While I am trying to get in, someone else goes down ahead of me.” Then Jesus said to him, “Get up! Pick up your mat and walk.”
At once the man was cured; he picked up his mat and walked.
John 5:5-9
It is perfectly reasonable to respect our time and to manage other people’s expectations of us. Boundaries are good for all parties. Moreover, it makes for a healthier, happier relationship. A lack of boundaries invites a lack of respect and that, my friend, is a relationship killer!
Do yourself a favor and endure the 90 seconds of discomfort it takes to start the conversation that leads to a healthier relationship. Say what you mean, and mean what you say. Just don’t say it in a mean way.
Come from a place of being rooted and grounded in love and grace and the conversation will go well. If you find yourself being harsh when setting a boundary, it is because you let it go too long. Soften your stance. Moreover, say your peace in a peaceful way.
Squirm if you must, but do yourself, your friends and family a favor and forge ahead to a better relationship and a happier life.