Effective CPR is a team effort because it is physically demanding and requires a number of individuals to work other elements of the problem set (airway, medication and access, AED, relief for CPR practitioner, communication with emergency department, police etc...). There is an awful lot to do in these situations and the scenario balloons in players from the first rescuer to the receiving emergency department. The goal should really be continuous motion to a higher level of care vs. getting frozen in place.

I will also note that it is pretty emotionally demanding, particularly given that it's likely to fail, and be coincident with someone else in distress (family member, friend etc...). This is an event you're going to want to put into a box and give yourself some time to work with.