"We will have to learn from the pain of the journey Munster have been through in this tournament, learn from the hurt of losing. Munster bossed the game and bossed the second half," said O'Shea.
"It was evenly poised at half time and the game could have gone any way. But those first 15 minutes of the second half were a car crash for us. We gave away five penalties, four of which were kickable, and that gave them the momentum and really got their crowd going.
"They brought a huge amount of physicality to the game and we were never able to hold onto the ball. Paul O'Connell was majestic, the man behind whom everyone else in the Munster team rallied.
"Every bouncing ball seemed to go their way and they won all the 50-50 contests. But we can't feel sorry for ourselves for too long because we can't afford to let all we have done this season drift away.
"We are in the top four in the Premiership and we want to defend out title. We just need to get our game going and we didn't do that today and the better side won."