Some time ago I got certified to be a yoga teacher. As a teacher sometimes I walk up to students and adjust their pose for optimum alignment. This means I put my hands on their body.
Many people love being adjusted or touched. Many people do not want it.
Let me take it a step further. Many people who love being adjusted and touched have days when they don’t want to.
In other words, just because I have always touched them does not mean I always can.
Each individual has his or her boundaries. I cannot fudge them, negotiate them, argue them, push back on them. I cannot require or demand an explanation.
Before I touch, I ask.
Your boundaries - even when they move, even when they change, even when they are seemingly capricious and inconstant - are your boundaries. You don’t ever need to justify, explain, elaborate or rationalize.
They belong to you and as such they can be anything you want.
The clearer your boundaries are, the healthier your relationships will become.
Related:
Dushka Zapata's answer to Why is establishing healthy boundaries such a painful process?