If you are the captain you can feel safe in the cockpit if you feel confident in your decisions because of your experience and aircraft knowledge. Sometimes decisions involve variables that can change like weather and multiple failures so you must always be prepared to change the plan if conditions require it.
FO's need to feel comfortable in the aircraft and not ever need the captains assistance in my opinion. They should fly like they are the captain and not let the captain make all of their decisions for them. Most of my FO's did that but with a few I didn't feel it was safe to take a restroom break.