The Dutch defender told avfc.co.uk: "The team spirit was always there but maybe not the belief. That came this season and was very important. If you don't believe you're going to win games then it won't happen.
"In the past my view is that we didn't believe we could win a lot of games. We're totally different now and hopefully that will continue. Belief is very important in football."
Bouma, who was a mainstay of Martin O'Neill's Villa side last season, added: "I'm pleased that I started every game because I had some problems in the past with injuries. I've shown that if I can stay fit I will play a lot of games."