General Alternatives:
* Peaceful reflection
* Serene contemplation
* Quiet introspection
* Mindful stillness
* Tranquil meditation
* Solitude and thoughtfulness
More Specific Alternatives:
* Deep thought (emphasizes intellectual focus)
* Spiritual stillness (emphasizes a religious or mystical connection)
* Inner peace (highlights a state of emotional calm)
* Moment of reflection (highlights a brief pause)
* State of grace (implies a sense of divine favor)
The best choice will depend on the context of your writing.