The 23-year-old made an impressive start to life in the Premier League with two goals in his first six games but since then has struggled to make an impact.
The Japan international has recently returned to action after being sidelined for 10 weeks with a knee injury and says he needs to contribute more to the team.
|STILL TO SHINE?
|KAGAWA AT MANCHESTER UNITED
"I'm not satisfied with what I have done here at all. It's a big and really famous club in the world and I need to overcome lots of pressures and be mentally stronger.
"Unfortunately I got injured, but I have to be better and grow as a player a person, in terms of contributing to team's wins and succeeding here."
The former Bundesliga Player of the Year has backed himself to improve, insisting he can emulate the mental strength shown by United's established stars to ensure he is not considered an Old Trafford flop.
"I really feel that we have a strong ability to bounce back when we are behind, so people in this team must be really mentally tough," added Kagawa.
"We have a really strong squad with many world class players, so it's lucky for me to have opportunity to train with them and play games with them."
Kagawa also hopes to draw inspiration from Manchester United supporters and manager Sir Alex Ferguson, who he was quick to praise.
|SHINJI TO SCORE?
|5/4||Shinji Kagawa is 5/4 to score anytime against Fulham in the FA Cup with bet365|
"Sir Alex is one of the best managers in the world," he continued. "What I am really impressed [with] are the numbers of great players he has helped to grow, the numbers of titles he has achieved for the team almost every year, and his ability to mould top players into a team.
"Also, the atmosphere supporters make at Old Trafford helps the team to fight back. As I said, my team-mates are so experienced and mentally strong."