Often, the students who resist new ways are the loudest or the most problematic in terms of classroom management, while the students who are happy with your new methods are quiet about their feelings. A simple feedback technique is useful to find out how many are with you, and how many are not. With the students, generate on the board a list of the teaching strategies you use, such as group work, work with manipulatives, working at the board, lectures, field trips, tests, assignments, etc. Ask them to list them and consider how useful each strategy is in helping them learn math. They could indicate "very useful," "somewhat useful" or "not useful" for each strategy. Ask them to hand in their papers with no name attached. Calculate the responses for each strategy, and report to the class the next session. You may find that most of the class thinks that a particular strategy is helpful, even though a few protest loud and long when you bring it out.
Knowing I have allies in the class, albeit silent ones, helps me persevere in using a given strategy, in spite of vocal protests. Furthermore, reporting back to the class, so everyone knows where we stand on the issue, helps too. I can be firmer about using the strategies many students find useful, in spite of resistance, and it gives me a chance to acknowledge the feelings of discomfort and resistance I know are there. For example, I might say to the class, "On the feedback sheets yesterday, 2/3 of you said going to the board was useful. So I'll be asking you to go to the board two or three times a week. I'm hoping that those of you who don’t like it very much will put up with it because other people find it useful. I know now that many of you are reluctant when I ask you to do it, and I’d like to figure out some ways to make it more comfortable, while continuing to do it. Does anyone have any ideas about how to make it more comfortable?”
Student resistance will weigh you down and tire you out. If you don’t deal with their resistance, and get them onside with you to work in new ways, their resistance will win. You may give up entirely and go back to teaching in ways you know are ineffective, because that is what students expect you to do.