老师好，最近在读The Aim of a University Education（By John Henry Newman十九世纪英国宗教领袖、教育家约翰·亨利·纽曼）时，对其中一句的which,it,its比较困惑请老师解答，非常感谢！

He is ever ready, yet never in the way; he is a pleasant companion, and a comrade you can depend upon; he knows when to be serious and when to trifle with gracefulness and to be serious with effect. He has the repose of a mind (which) lives in (itself), while (it) lives in the world, and (which) has resources for (its) happiness at home when (it) cannot go abroad.