Sermons about tithing focus on giving money to God. How 10% of your income belongs to God as an indication of how He should be controlling all of your income. I have yet to hear a pastor spend time talking about how other behaviors can negate tithing. I know for a fact (from personal experience and observation) that poor money management regardless of how much you tithe negates the benefits of tithing. If you habitually steal from others it too negates the benefits of tithing. If you're greedy or give out of selfish motivations these negate the benefits of tithing.
So when you go to church and are listening to a sermon remember that the pastor is presenting a fraction of the topic. He or she is offering a microscopic view of a big issue. No sermon should be taken at face value but rather it should be used as a beginning place for personal investigation and prayer. The pastor is presenting principles that are intended to help you grow in your relationship with God but listening to a sermon never helped anyone's relationship grow. It's only through meditation, study, developing a personal relationship and application of biblical principles that is motivated by a love for God that real growth takes place.