appropriate team interaction makes design goals achievable

... and assertiveness, is a major element... see why. the assertiveness model goes as follows: "Assertiveness lies in the middle of a continuum of behaviour towards others, that the Backs defined in terms of how we recognise the rights of the two parties involved. Aggressive - You exert your right to have ideas and opinions at the expense of the other person's rights. In fact you behave as if the other person's rights don't matter. Assertive - You exert your rights freely and clearly, but at the same recognise the other person's rights to be heard, to have pride in what they do, etc. Non-Assertive - You take too much account of the other person's rights, to the extent that you forego some or all of your rights to express ideas or influence events." check out current management topics as well.

there's no need to state the obvious about the poor state of design management, and the widespread inability of designers to be good managers. Also, see why we shouldn't feel guilty saying no sometimes, and why people skills are paramount to achieving the highest standard of design. A group i found whilst googling a review of 'seven habits' for another post earlier have a very interesting knowledge page.