Pitchers who take their time walking around, rubbing the horsehide to death, then take that deep breath and let it out before every pitch are just dealing with nerves. Same thing with batters who adjust their batting glove, shake their head, study the grain in the bat.. and so on, are just dealing with nerves. All in all, it helps settle a man down a bit.
Pro ball at the Majors level is pure pressure, grinding, gut wrenching pressure. The slightest tick off the park by someone somewhere who finds any reason to "pull the plug" on a guy - will do so. It's a painful existence and not for the faint of heart.
I think baseball is a pastoral game to be watched and enjoyed for the leisure of it, then for the explosive spontaneity of it all. The jockeying for any advantage is a suspense all in itself.
I use to enjoy sitting back in my folding metal chair, rock on the back two legs and watch from my vantage point in the bullpen, all the "what if's" going up in smoke as opportunity after opportunity ether came true or when down in smoke. Then I'd get a chuckle out of the young guys biting at the bit to get in, while the older guys would silently sit and whisper to themselves ... oh crap, don't call me, don't call me..".
This is a hurry up and get it society. I'm glad I'm out of the business. Very few seem to enjoy the game for what it is and what it isn't. I kind of miss the days (nights) when a jumping foot under my chair gave away my nervousness because I suggested something that was actually being tried, when a bottle of Kaopectate was always in my desk, and extra innings had a kid who jumped seats leaning against the rails waiting for what could happen next.
I guess I'm comfortable with the way things use to be - take your time, enjoy the moment. But then again, I didn't have to worry about the fan's moment of "I want it now."