The self-transcendence which belongs to the principles of sanctification is actual in every act in which the impact of the Spiritual Presence is experienced. This can be prayer or meditation in total privacy, in the exchange of Spiritual experiences with others, in communications on a secular basis, in the experience of creative works of man's spirit, in the midst of labour or rest, in private counseling, in church services. It is like the breathing in of another air, an elevation above average existence. It is the most important thing in the process of Spiritual maturity. Perhaps one can say that with increasing maturity in the process of sanctification the transcendence becomes more definite and its expressions more indefinite. Participation in communal devotion may decrease and the religious symbols connected with it may become less important, while the state of being ultimately concerned may become more manifest and the devotion to the ground and aim of our being more intensive.Here, then, we have Tillich's spirituality in a nutshell. Self transcendence is only on aspect of the process of life in the Spiritual Presence, but it seems it is the most important one. Tillich stresses how the Spiritual Presence becomes a part of ordinary life, not a specific area of it.
Systematic Theology III, 236
However, and I think this is the first time I have expressed criticism of Tillich in this series - I have obviously choses the quotes I like - I think the notion that the natural development of spiritual life is away from the communal devotion towards a more individualistic spirituality.
I see where he is coming from, and I think it is rather usual that spiritually mature people - in protestant traditions - tend to have a rather detached relation to services and liturgy. But I'm hesitant to make this a part of the system as Tillich does - I would prefer to place this under the heading of ambiguities of religious life. It is the way communal service is acted out under the estranged state of existence that communal service lacks meaning for the spiritually mature. The notion community is part of the essential being, and this too should be reconciled with existence under the influence of the New Being.