The Argentine admits last season's European exit still hurts but is keen to make up for that disappointment this time around
The Blaugrana were drawn alongside AC Milan, Celtic and Ajax in Group H of the competition on Thursday as they bid to go one better than their last four exit in 2012-13.
"Last season was good for the club, because we won the League against a team like Real Madrid," Messi told reporters.
"It was a major title, but we lost in the Champions League badly against Bayern Munich. Anyway, you have to keep positive and hope to do great things this year."
The 26-year-old also acknowledged the difficulty of facing Celtic and AC Milan again, having been beaten by both sides in Europe last season.
"As always, we have been drawn into an even group," Messi told reporters.
"The opponents are already known and difficult to play, as we expected.
"Against Milan and Celtic we already played last year. With Ajax it is the first time, but we also know them.
"As always, the club is required to win it all. And for that we are preparing, but each year is harder, because all teams reinforce and are getting stronger."