Instead the Swans manager had to be content with leaving Lonon Road with just a single point despite the side coming from a goal behind to lead 2-1 with just moments of the game remaining at London Road.
Sousa was also unhappy about Posh's opening goal - he felt that Gorka Pintado had been fouled in the build up to Chris Whelpdale's goal.
"There was only one team with the mentality to win the game," Sousa said after the 2-2 draw.
"We produced all the football and did everything we could to get the three points.
"I do not feel we deserved to be behind anyway.
"Anything can happen at a throw-in like the one for their first goal and in my opinion there was a foul on Gorka Pintado from behind.
"It is not a fair goal but my team showed a good reaction to come back and score two goals to get ourselves ahead.
"But we have to show more maturity after making such a big effort. It is very disappointing to leave with only one point."