There are multiple senses being asked for in the question. I will provide an expression that satisfies the following:
You know what you want, you are at peace with yourself.
comfortable in (one's) own skin
[The Free Dictionary]
Displaying a relaxed confidence in and clear understanding of oneself and one's abilities, especially when presenting oneself to or interacting with other people.
Though his girlfriend's group of friends are all older and more established in life, he is comfortable enough in his own skin to have no problem mingling with them at parties.
Janet is so comfortable in her own skin that I have no doubt that she'll find her ideal path in life.
From "Comfortable in Your Own Skin" by Risë Rafferty:
What does it mean to be comfortable in your own skin?
What does that look like? I recently asked these questions to my youth Sabbath school class. We briefly remembered awkward adolescent stages of our lives in which we weren’t so comfortable and then pondered its definition in the word and in the lives of people we know.
Some of the definitions the class threw out were:
- don’t want to change anything about yourself
- comfortable to be and express what is on our minds
- don’t care about what people think
- non-conforming to other people’s standards
- healthy self-confidence
- unafraid to be uniquely ourselves without conforming to another's idea of who we should be
From "How to Feel More Comfortable in Your Own Skin" by Margarita Tartakovsky:
We become truly comfortable in our own skin when we accept ourselves—even the dark spots we don’t want others to see, said Ahmadinia, who specializes in mindfulness, stress and trauma at the West Los Angeles VA. We “see ourselves completely, as we are, without trying to avoid, run away or resist.”
From "How to Feel Comfortable in Your Own Skin" by Mary Dunlop:
Take time out to nurture your spirit, whether that means practicing yoga, walking on the beach, or simply relaxing. In order to be comfortable with yourself, you first need to be comfortable just being.
From "How to Become Comfortable in Your Own Skin" by David B. Bohl:
Other tips: stay positive and active. Simplify your life. Regain control over your hectic schedule. When we set our day’s goals and focus on a greater meaning and purpose for our lives, we are on our way to true success: happiness. People who are genuinely happy feel at ease with others and comfortable in their own skin.