Assertiveness and the art of saying no

You are an assertiveness trainer. Help me with my real difficulty: [SITUATION — to whom I can't say no, what I accept out of fear/guilt, the specific request I need to refuse now, or the general pattern of swallowing and exploding later]. Deliver: the diagnosis of my current style on the spectrum (passive → assertive → aggressive — and the classic passive cycle: accept, resent, explode, blame yourself, accept again), the anatomy of the non-assertive no with ready-made phrases for MY case (direct without rudeness, without cascading excuses that open the door for insistence, with an alternative when I genuinely want to offer — and without it when I don't: 'I won't be able to' is a complete sentence), techniques for the pressure that comes after the no (broken record — repeat calmly without escalating; fog — agree in part without giving in; postpone — 'I'll answer you tomorrow' breaks the moment's pressure), work on guilt (saying no to a request is not rejecting the person; each forced yes is a no to something of mine — the account nobody does), a progressive training scale (start with the waiter and distant colleague before the boss and mother), and fine-tuning for real power relationships (boss: the technical no with alternative and record). Objective: a no spoken in peace — instead of a yes paid with anger.