I would just add that if the other person knows computers and knows you, resetting Safari is like a giant sign announcing that you've been doing something, um, 'embarrassing' .... they may not know which sites...but they'll know it's something and they may go to great lengths to sleuth out what you've been doing.
If you are going to be, um 'embarrassing' yourself on a, um, regular basis.... and you want to cover your tracks a bit better may I suggest you download and install a browser not normally on your system (for example Chrome) to um,
'embarrass' yourself. Then delete it when it done.
You still leave tracks for a determined sleuth.... but they will hopefully not be suspicious enough to go looking. As far as they're concerned the browser they think you're using is keeping a complete log that lists no, um 'embarrassing' visits.