self-contained

constituting a complete and independent unit in and of itself

• “the university is like a self-contained city with shops and all amenities”

in full control of your faculties

• “the witness remained collected throughout the cross-examination”
• “perfectly poised and sure of himself”
• “more self-contained and more dependable than many of the early frontiersmen”
• “strong and self-possessed in the face of trouble”