Pain is the emotion that attends loss.
Loss is the absence of a perceived good.
What is a perceived good?
Something in the world (a person, a circumstance, a thing, a state of affairs, an image, an idea) that I am relying on for my happiness.
There is nothing wrong with those things, and there is nothing wrong with appreciating or enjoying them.
The attachment to the thing is the problem.
A wooden statue is not an idol until it is prayed to.
Pain is therefore a sign of idolatry: the worshipping of something other than God as my source.
Attachments are invisible until threatened.
Pain is therefore necessary to identify my attachments, so I can redirect my reliance to God.
Anything that stops me from feeling pain, whether an activity or a substance, illicit or legitimate, will stop me from growing.
Growth requires presence to pain, and the willingness to feel it, come what may.