It is very natural that we find it very hard to say NO to someone; or at least people like me finds it rude to say NO. Unless of course if you care less about what others think or about their feelings. It is very important to say NO sometimes, as saying YES to something you know you will not be able to accomplish will ruin your reputation in the long run or will give you unnecessary stress.
So, how does it affect Project Managers? Almost every day they face this indecision whether to say Yes or No and struggle to find an in between approach. I asked few of my fellow PMs about how exactly they deal with it; and all of them said it is hard as the path we are looking is disagree without being disagreeable. Using the correct words while disagreeing is very tough as not everyone is understanding or willing to listen to your side of the story.
Client wants multiple tasks to go LIVE on a Friday evening, developer requests you to approve his leave when you know multiple deadlines are coming, CEO asks you to take on couple of more projects when your hands are already full, these are just some of the scenarios we face on a daily basis where we want to say NO, but struggle to say so.
One approach that works to certain extent for me is trying to buy time; instead of giving an answer right away; I would say give me few moments, let me review it and get back to you. It gives me time to gather my thoughts and prepare a better answer. The other day, one of my client asked me to deploy 2 big tasks on a Friday evening. If I had said NO to him he would have been upset and get into an argument with me. But I said, let me get back to you on this. Then I wrote him a nice email after half an hour saying we can definitely deploy, but as there is no quality assurance team available at this moment or over the weekend to test it and if anything happens then I do not have anyone on call to fix it either. If that is okay with you, then I am ready to deploy. Within seconds, reply came in HOLD all deployments till Monday morning when you have the full team available. I could have said this on first conversation, but taking some time made him realize that I did investigate on my resources and even though I am not saying I would not deploy but I made him say NO, instead of it coming from my end.
It is an art itself, and it is possible that on first few instances you will actually appear to say NO while trying to delegate the situation or will take the bait from client and end up saying YES. But the more you will try, the better you will get at it. One thing to remember though, you should not make it a habit to say NO all the time, as everyone likes a YES person.