Man, I gotta push back on that two hour rule a little. Waiting that long on a heavy lift is just asking for trouble. My rule is if I even have to think about whether I need help, I already do. Pride heals way faster than a torn muscle or a busted disc.
Make a hard rule to ask for help after two hours of struggling on your own. It keeps small issues from blowing up into bigger problems. Be specific about what you need, like "can you spot me on this lift" or "show me how this software works." Most folks are happy to assist once you actually speak up.