The nature of polarization fatigue in BiFeO3 is revealed using monodomain epitaxial thin films with different orientations. We have found that the fatigue strongly depends on switching path. Fatigue-free behavior is demonstrated in ferroelastic switching (71 degrees and 109 degrees). In contrast, a significant polarization fatigue occurs in ferroelectric switching (180 degrees), which involves multiple switching paths and formation of charged domain walls that effectively pin domain walls and hence reduce the total switched volume.