NOOOOOOOOOOOOOOO means no and can also be used when you're refusing to do anything.
Wait before giving an answer. If saying yes is your default response, then simply giving yourself some time to decide lets you consider what would be involved in saying yes and whether you really want to. Try it: “Let me check and I’ll get back to you.
Never say maybe. Have you ever said maybe I’ll stop by when you knew you wouldn’t? If it’s really a no, then say no, not yes or maybe, which will just create guilt or stress for you, and confusion for others who don’t know whether to believe you. Sorry I won’t be able to make it. Hope it’s a great time.
Don’t over explain. Most of the time, the person making a request or extending an invitation is mostly concerned with their project or event. They don’t need or even want to know why you’re saying no, because they are already thinking about who else they’ll invite. Once you’ve decided you don’t choose to do something, that’s the only information that matters. Other commitments or full calendar might be a different meeting, your writing time, or time you set aside for grooming your cat. It doesn’t matter what your priorities are. Don’t put your decisions on the table for other people to evaluate. I’m sorry, I have another commitment that afternoon and won’t be able to attend.
Acknowledge the other person. Sometimes we say yes to things because we’re loyal to a particular person, group, or cause. Being sure to acknowledge them or the project lets you express support or enthusiasm without saying yes to an event you don’t choose to attend. This sounds like a really worthwhile event. I’m sorry I won’t be able to attend.
Offer an alternative or a resource, but only if you mean it. If you don’t want to go out this weekend, but would like to next weekend, say so. If you know someone else who could contribute skills to the project, suggest their name. I can’t take on this commitment right now. but James might be interested, and I know he’s done similar work before. Do you want his email address?