save your project with different names. eg, if you start a fla with name adobe.fla immediately save as adobe_v000.fla. make whatever changes (no more than 1/2 hr worth of work, for example), then save as adobe_v001.fla. etc.
then if you corrupt a version, you can return to the previous version having lost, at most, 1/2 hr worth of work. pick a save frequency that works for you.