Urge to Work Crime

I have faced it in the past. Am facing it now. Think will repeat it in future also.
The Crime of a Project Manager: The urge to work and directly dive into the work specifics without stepping back a minute to document the scope, work definition and plan .

Inspite of a proven success formula in a number of projects that go well with planning, there is the occasional "fast drive in traffic lane" mentality that sets in. The projectStand gives a good ambience and inviting to dive into work and deliver fast, without scope, work definition and plan.

Typical ambience factors that sets up for fast drive in traffic lane are :

1. Project is already in advanced stage and you are invited to carry forward "a small" portion with special skills that team has.
Fast drive in traffic lane: Getting carried by the word "small" and committing in the impulse of the description of "small" happens many times.

Only to realize later that "small" is the reason the work has wriggled out of hand easily.

2. Project requires Integration work where same set of files are to be used by 2 different teams reporting to 2 different managers.
Fast drive in traffic lane: It is always found wanting in such projects that one person from either team needs to interface between teams catching the work that falls between the boundaries. Because project matters, my team ends up overstepping their border of work to ensure smoother hand off. In the cross-over the team find themselves in a different territory to help other team's work.

Be careful in this lane as this would be demoralizing if only one team knows what camaraderie is. The ignorance of camaraderie with other team is unpardonable.

Eventually it is found that the same time is used effectively by smarter colleagues who leave no time in redrawing the borders farther from the new territory. In eventual blame game, I get caught on the right side wrongly.

3. You consider your peer manager the lead on the project and expect to be accountable.

Fast drive in traffic lane: The biggest mistake is this one and the crime is that you do not trust your self. This is the worst trap that leaves a bad taste compared to the above two.

Begs repeating again: The biggest mistake is this one and the crime is that you do not trust your self. This is the worst trap that leaves a bad taste compared to the above two.

Trusting people is my forte and for few incidents like this, do you think I should be paranoid with general public ?

Why is it that Heroism in the world is potrayed as faster action doers and impulsive risk takers ?
While people who think fast, time their responses (plan), communicate with a humor sense (work definition) remain comedians and soldiers in the management game ?

Which side are you - Hero or comedian. Me prefers a comedian role.