In the lunge- as in all level-change variations- brace before you drop; Soft, is sketchy!
Set posture, step back far enough to ensure the front knee does not move forward of the front foot, and drive hard into the ball of the back foot in the descent.
Climb back up by driving as hard as you can into the heel of the front foot!
Reset, and, repeat! Keeping an upright torso in unweighted variations goes a long way in making sure we do the very same when under heavy or unstable load.