Short answer
When an elderly parent makes you feel guilty, the guilt may not be a reliable sign that you are doing something wrong. Sometimes it is a sign that an old family role has been activated.
You can care about your parent and still need the calls, visits, money, errands, or emotional demands to become more manageable.
Guilt can sound like love
"After everything I did for you."
"I guess I will just be alone."
"You are too busy for your mother now."
"Your father would never have treated me this way."
These sentences may come from real loneliness or fear. They can still place you in an impossible position: prove your love by giving more than you can sustain.
Why it works so quickly
Guilt usually knows the old door.
If you grew up being the responsible one, the peacekeeper, the translator, or the child who noticed everyone's mood, your nervous system may treat a parent's disappointment like an emergency.
That is why the boundary can make sense in your head and still feel unbearable in your body.
A useful distinction
There is a difference between guilt that teaches you something and guilt that keeps you trapped in a role.
Helpful guilt says: I caused harm, and I need to repair it.
Role guilt says: Someone is upset, so I must abandon myself until they feel better.
What you can say
You do not need a perfect script. You need a sentence you can repeat.
"I hear that you are upset. I can come on Saturday, not tonight."
"I am not able to talk about this three times today. I will call tomorrow."
"I care about you, and I am not able to be the only plan."
"I can help with this piece. I cannot take over the whole thing."
When therapy can help
Therapy can help you understand why a boundary feels like betrayal even when it is reasonable.
Often the work is not finding the perfect words. It is becoming able to survive the guilt that follows them.