Becoming an assertive person is a life-long process and requires trust in yourself, not only in the beginning of the process, but down the road as well.
It is a continuous process that starts in self-knowledge. It takes practice, and it would be helpful to start practicing in easy situations in order to develop the necessary self-confidence. In time, you will gradually be able to handle even more difficult situations.
If you want people to respond to your ideas and needs, then you should say what you want in a way that will make others respond. When assertiveness is a familiar behavior, you will not need to use techniques to do it. As long as one is practicing, they are likely to build more self-esteem. The best part is that other people will recognize that you respect yourself and will behave, in turn, with respect. Self-esteem is perhaps one of the most basic aspects of a harmonious relationship with yourself and an important precondition for having a high self-esteem.
It requires us to accept ourselves. Besides, accepting others requires us to have accepted ourselves first. If you cannot accept yourself, you cannot leave room for third parties.