Rolling targets, changing scope, and an unprepared project lead sounds like the norm for most of the places where I have worked. The ticket to not feeling stress is to do three things.
1) Stop giving a shit. This solves lots of problems. If the project succeeds or fails is not your problem. What people say/think about you is irrelevant.
2) Do not start putting in extra time just to make up for others mistakes. If *you* screw up, then you fix it regardless of the time and personal cost to you, but if someone else screws up, then its not your problem.
3)Learn to say no in a way that does not get you fired. IE: "Fuck you, I'm not doing it" is not appropriate. However: "I have prior commitments after work and I will be unable to stay late tonight. I will attack this first thing tomorrow morning and give you a status update by early afternoon."
Very few supervisors want to actually come in, look you in the eye, and tell you that you *have* to stay late after you have said you other things going on. No one can make you stay late, and I've never heard of anyone getting fired for not consistently putting in more than 40 hours. Hiring and firing people is expensive. High turnover makes the boss and the company look bad.
That's why they call it WORK.
Work is not always pleasant. If you don't run the place, you can't always choose your assignments. You don't always get to team up with your favorite or the best coworkers. Some projects have ridiculous deadlines. Some clients or bosses have ridiculous expectations, etc., etc.
The best way to handle crappy jobs is to attack them, knock the work out quickly and put it behind you.
Suck it up and do the job to the best of your abilities or move on to work elsewhere.
Good stuff here. I find the best way to reduce stress is to document things clearly.
When meetings come, document the scope. I mean really - write it all down, then followup with an email to the team after. This can avoid "scope creep" (and make sure on the email list is the boss of the person in charge).
Also, document the specific steps needed to reach the goal. Break it into baby steps.
If schedules are involved, write up a realistic schedule.
Now, this is probably not your job - this is probably the job of the person in charge. However, some people suck at that, and I find if I make the schedule, it covers my own ass.
I recently got put in a project late in the game, and suddenly, there was a big fat rush to finish things by a deadline. I did not create the deadline. I did not pick the date. I was not involved, or I would have worked backward or forwards and told them it was impossible. So when we got close, I said "I will do my best, but I did NOT pick this date and I do NOT have control over the rest of the work. I do not have the power to make the vendor work faster".
I find being up front about schedules with everyone is helpful. We cover them weekly.