These words of mine may guide you into an assertive trance. That is deeper than just thinking "be assertive". It is a feeling of being assertive. It is finding a sense of assertiveness that fits you like a glove.
Assertiveness walks on two legs: firm and fair. Assertiveness is firm not harsh, it is firm and not yielding. Assertiveness is fair to you and your needs. It is also fair to others and their rights and feelings.
Let a feeling of firmness arise. Let it fill you and enfold you. It is not like a coat of armour: hard and frightening. It is not like jelly that will wobble and break up.
Find your OWN feeling and picture and sense of firmness. I once had a young female client who had seen another hypnotist. He had given her confidence. Of a sort. She said it felt like wearing a heavy male overcoat. Just like the one he had on his door. She found it very uncomfortable.
You, too, could find someone else's sense of assertion uncomfortable. In this trance you are hunting, or shopping for, or creating your own.
Now start looking for a feeling of fairness. How can this feel to you? Perhaps it is a bit like friendliness. You can remember times when you have been treated fairly. You can remember times when you have been fair to someone else. Let those memories help the feeling of fairness to fill you Fairness is not rushed. It takes its time. Fairness is not loud. It is moderate in tone. Fairness does not do all the talking. It listens well. Let a feeling of fairness become a mood that you can slip into easily.
Let ideas of assertive people you admire enter your mind. Look at them when they are with others. See how they act. Hear their words in your head. Listen to them talking. They are firm. They are fair. They are well balanced. Do not waste time thinking of people who are assertive, but not in a way that suits you. Do not wear clothes for your soul that do not fit. Think of people who are firm in a way you would like to be firm. Think of people that you respect if they are firm with you. Remember the fair ways of those who are fair in a way you would like to be fair. Recall the ways in which you like people to be fair to you
Let the words "firm and fair" be woven through and through your assertive state. Every time you think those words let the mood and all it means to you return to you. In future whenever you are dealing with a difficult person, think "firm and fair". They may be angry. You will remain "firm but fair" They may be irritating. You will feel better staying "firm and fair" They may have no idea of self-control. But you will not copy them. It is much more effective to wear your own assertive mood. They may have no habit of listening. Why copy their bad manners? They may be totally selfish. If you are firm and fair you will firmly stop them taking advantage and not rouse them to be yet more selfish. You will be fair to their selfish needs. You will handle them effectively. However badly they behave, firm and fair is your best reply. For you to be assertive, neither a wild boar or a frightened mouse, is best for you.
Each time you meet someone you can practice your skills. Before a meeting you can mentally put on your assertive mental clothes. Afterwards you might think of ways you might improve them. Each day you can make an easy assertiveness more a part of your nature. Your own nature. Your own natural assertiveness.