What is assertive communication?
Assertive communication is when you confidently express your needs and opinions in a fair, honest and calm way whilst considering the needs and views of other people.
It’s an important skill that reduces stress because it allows you to:

• Stand up for yourself
• Say “no” without feeling guilty
• Express your wants, needs and opinions
• Maintain self-control
• Judge the situation and be assertive only when it’s appropriate

The three communication types
There are three different types of communication styles:

Passive
Assertive
Aggressive

Not saying what you think
Expressing yourself clearly and confidently
Shouting, aggression

Scared to speak up, others attack you
Speaks openly and honestly
Interrupts or talks over others, attacking

Avoids eye contact
Maintains eye contact
Stares, looks judgmentally

Speaks softly
Speaks firmly and at conversational level
Speaks loudly

Reduces your self-esteem
Increases your self-esteem
Reduces others’ self-esteem

Gives in
Compromises
Takes

Believing that your own needs don’t matter
Believing that everyone’s needs are important
Believing that your needs are the most important

Unable to say “no” – you feel guilty if you do
Says no in an appropriate fashion
Says no in an angry and reactive way

Makes body smaller e.g. slouches
Relaxed and welcoming posture
Closed posture, makes body bigger, invades personal space

For example:
A colleague approaches you and asks if you can attend a meeting in their place because they’ve double-booked themselves but you have a list of work you need to urgently get through that day.
An aggressive person: “Absolutely not. You always do this! You need to learn to manage your own workload rather than bothering me!”
A passive person: “Yeah of course I will.”
An assertive person: “Unfortunately I can’t attend the meeting because I’ve got lots of work to get through today, perhaps there’s someone else you can ask.”
Source: https://virtualspeech.com/blog/assertive-communication-reduce-stress