The intention to make One with the spear efficient is holding him back. He hasn't found the answers to the questions he wants to solve and every attempt to solve them is being foiled by SQUARESKULL's overwhelming prowess. No matter what he tried, it all ended in failure. SQUARESKULL was a superior enemy and Soverick couldn't let his body act recklessly against one. That never ends well.
He wasn't angry at SQUARESKULL. His body might be broken and in pain but his mind has never been better. He had learned a lot from their fights. So he wasn't angry at SQUARESKULL, even though he knew that SQUARESKULL cheated to beat him. He won't whine about the defeat. Instead, he will learn from it and beat up SQUARESKULL one day.
"Maybe you're right. You need an opponent that you can beat. Go to the arena and fight someone. That's after you have healed your wounds."
Then SQUARESKULL turned to leave.