It's not a punishment in Catholicism either. It's about getting a fresh start, healing the once devastated relationship with God. Devastated through mortal sin.
This idea of penance as a sort of torture is a gross misunderstanding commonly held by protestants.
We're absolved even if we don't do our penance, it's not attached to the forgiveness of sins.
Even when punitive, Orthodoxy is so voluntarily... Here is an example:
A monk was attending Vespers one evening. He hadn't bathed in awhile, and was singing in the choir when a fly buzzed his eyes and ears and landed on his nose. He killed the fly with a very quick slap. He then stopped singing, and said to himself: "I have struck out in anger again..."
He immediately departed from the Service and walked down the hill from the Katholikon to a slough there and took off his cassock and stood in prayer for three days, letting all manner of biting and stinging thing torment him without resistance. When the 3rd Vespers Service arrived, he put his cassock back on and rejoined the Service and went on about the rest of his normal evening prayers...
The ONLY relevant question now is this: "Did he EVER strike out in anger again?"
And a VERY relevant answer should be: "I certainly hope not!"
Will he be tested in his new resolve?
Absolutely most assuredly...
So was he concerned about offending God?
Of course!
But his primary concern in that event was his own sin...
There was no concern for assuaging God's feelings of offense at his action...
But his sole concern was the eradication in his own person of his own attraction to that sin of striking out in anger which had been plaguing him throughout his life...
There is NOTHING LIKE this great and wonderful Faith of Christ!
Christ did no sin at all and suffered silently in His Passion...
Consequences self imposed for sins can be a good thing...
Marvelous reminders in sin's treacherously seductive beginnings...
Arsenios