Short answer: a polite no in English almost always has two parts, not one. A short, honest reason or a warm line, then a clear no. Not three apologies stacked in front of it, and not a bare "no" with nothing around it either.
Most women learning English do one of two things when they want to say no. They over-apologize until the actual no gets lost, or they say yes because they cannot find the English fast enough to say no the way they would in their own language. Neither is a vocabulary problem. Both have a fix, and it is shorter than you think.
In your own language, you already know exactly how much softening a refusal needs, because you have heard thousands of them your whole life. In English, you do not have that same library yet, so you either guess too soft, which turns into a yes you did not mean, or you guess too hard, which comes out blunter than you intended. Neither is really about your English level. It is about not having the actual pattern memorized yet.
That pattern is simpler than it feels from the outside.
English speakers soften a refusal with one short move, not a paragraph of apology. The two most common patterns:
Reason, then no. "I already have plans that night, so I can't make it." The reason comes first, the no is short and clear, and that is the whole thing.
Warm line, then no. "I'd love to, but I can't this time." The warmth signals you are not rejecting the person, just the request, and then the no still lands clearly.
What both patterns skip is a string of sorrys. "Sorry, sorry, I'm so sorry, I don't think I really can, sorry" buries the actual answer, and it often makes the other person push harder, because an answer that sounds unsure invites a second ask.
For work and requests: "I wish I could, but I'm at capacity this week." "That won't work for me, but thank you for asking." "I'm not able to take that on right now."
For invitations and social plans: "I'd love to, but I already have something that night." "Not this time, but let's find another day." "Thanks for thinking of me, I'm going to pass on this one."
For a fast, in-the-moment no when you do not have time to build a full sentence: "Let me think about that" buys you a few seconds, and "I can't, but thank you" is short enough to say even when you are nervous.
The people around you start hearing your actual answer instead of hearing your discomfort. A short, clear no reads as someone who knows her own schedule and her own mind. A long, apologetic one reads as someone who might still be talked into a yes, which is exactly why it gets pushed on more often. This is not about becoming less warm. It is about letting the warmth live in one line instead of five.
This is also exactly the kind of moment my new course, Find Your Voice, is built around: not grammar drills, real practice saying the things you actually mean, out loud, until they stop feeling foreign in your mouth.
If the freeze hits you before you even get to the no, that is a related but separate problem, and I wrote about the fix for it here: why do I freeze when I have to speak English. And if this mostly happens to you in meetings specifically, see how to speak up in work meetings when English is not your first language.
Mistakes are the fastest teachers. The first few times you say no in English, it will feel too short, too blunt, too plain. Say it anyway. That discomfort fades faster than the discomfort of saying yes to something you did not want.
A bare "no" with nothing around it can land harder than you mean it to, not because the word itself is rude, but because English speakers expect a small amount of softening around a refusal. You do not need an apology or a long excuse. You need one short reason or one warm line around the no, and that is usually enough.
No, and over-explaining often makes a refusal sound less confident, not more polite. One honest reason, or none at all, said plainly, works better than three excuses stacked on top of each other.
Over-apologizing. Saying sorry three times before the actual no buries the message and can make you sound unsure of your own answer, which invites the other person to push back.
At work, a short reason plus a clear no is usually expected and respected. With friends, a warmer tone and an alternative, like suggesting another time, tends to land better than a purely functional refusal.
Find Your Voice is a new course built around moments exactly like this one, saying what you actually mean, in English, without the apology paragraph first.