Soft edged clone stamp tool brush size

Hi!

Is there anything I can do to fix this frustrating issue:

When I'm cloning with a soft edged clone brush, brush strokes will appear also outside the brush circle (because of the softness). Is there any way to make it work so that no pixels will ever be painted outside the brush size circle? The current behaviour is causing me a headache because I cant see when I'm too close to an area that I don't want to paint on -I can only quess when my paint circle is too close and I seem to be constatnly quessing wrong, thus painting some partly opaque pixels on areas I didn't want to paint on at all.

Any help will be greatly appreciated!