Bellecose
I know from experience how hard it is to change the you people expect to be met with when they ask for something like money. IME it takes incremental ‘re-training’ until they see you in a different light. To do this, you need to first see yourself in a different light.
I think the difficulty of assertiveness is underestimated. It’s a tricky balance to achieve. I’ve met many a person along the way who would define their aggressive behaviour as assertive...
I agree with BlankTimes that simply practicing saying no can be helpful. We’re conditioned to make excuses and just a simple no with no explanation can be powerful. (There’s no room for argument or negotiation)
Some good advice I once heard in relation to changing our own behaviour was to not expect to do it all overnight. Aim for incremental, 10% change. So maybe practice being assertive in everyday situations where the outcome isn’t so emotionally loaded. Eg ‘I prefer my coffee with less milk’ or similar rather than just accepting what you’re given. I think it takes off the pressure in terms of what you might currently see as ‘innate traits’ (they’re not) you have and helps you start seeing yourself in a new, assertive light. That then helps with the confidence to project yourself as such if that makes sense.
I think I’d also look at my own ‘belief system’ around money. eg do I feel safe with money, am I comfortable using it to meet my own needs etc? If you find something (like fear of not having enough, guilt for not giving it away etc) then work on telling yourself a new ‘story’ around it (eg money is energy, I will attract what I need, I am worthy of using this energy to nurture myself etc)
I’d look at self care (always central IMO) and maybe a ritual to protect your energy (working from the premise that money is energy too) along with the suggestions above to shift your mindset in relation to yourself as an assertive being x