First things first: how do you know you will love these lower-paying careers? Are you certain that you'll find them more fulfilling and more sustainable? Are you certain there are jobs available? Before you invest in a master's degree, go do some informational interviews with folks who are already working in these fields.
While I haven't transitioned from high pay to low pay, I have chosen a lower-paying career path out of many options available. I work for a nonprofit. If I did what I do in a corporate setting, I could certainly be making much more money. But the mission of my organization matters a lot to me, I love what I do, and I can see myself doing it for a long time. I have occasionally explored going corporate, but I've never actually followed through. Fortunately (or unfortunately, depending on how you look at it), my spouse shares my mindset. We do our best to keep our spending rate low and our saving rate high so that we can continue to do the work that is meaningful to us.