How can I communicate my needs in an assertive way?
I'd suggest using the acronym A-AID as a framework:
A, Acknowledge - What positives have happened within the situation that you can thank this person for?
A, Activating Event/Action - What has been done or said? Try to avoid using the word 'you', instead switching to the word 'I' where possible. For example, instead of saying 'when you said...', turn it round into 'when I heard...'. This is you taking responsibility for yourself.
I, Impact - How has this affected you? Emotionally and/or practically? It's best to try to limit this to only 1 or 2 things, to avoid overwhelming the other person & making them feel attacked! Try to narrow it down to the core problem.
D, Decide/Do - What would you like to change? It's helpful to think about this before, and to reflect on what your 'bottom line' would be.
Try working through this framework using a problem you're having or have had -- although I'd suggest not to pick a big problem to practise with!
For example, I'll go through A-AID for being invited to too many meetings:
A/A - I really appreciate that you value my opinion and have asked me to be present at this meeting.
I - However, at this current time I've got a lot of competing priorities! At the moment, my main focus is communicating with students, either on a 1:1 basis, on Unitu or through Instagram. Students have fed-back that they are really valuing this, and so it's something I'm keen to continue.
D - I understand the importance for you of gathering student views on this matter, and I'd suggest that you involve XYZ instead, who may have more flexibility in their schedule to be able to help you! You're also more than welcome to email me if there are any specific agenda items which you would like my feedback on.
Resources:
Handout from Springfield Hospital's Recovery College