We don’t work in vacuum. We interact with different people to reach our goals. Usually we’re organized in teams which have (or should have) the same goals. If we’re lucky we participate in goal-setting process.
And there a problem occurs. Most likely not all people engaged in goal-setting or any other decision-making process will agree. You shot with all your best arguments against the decision but still it’s made. What to do?
Actually if you feel you’re the part of the team, once the decision is made you should support it. Even if you don’t fully agree with it. If you push to different direction than the rest you shouldn’t be a team member any longer, should you?
Of course above is true as far as everyone has fair (for their role) impact on decision-making process.