General synonyms:
* Comfort
* Solace
* Relief
* Alleviation
* Mitigation
* Soothing
* Assuagement
* Ease
* Pacification
More specific synonyms:
* For grief: Sympathy, empathy, condolence
* For disappointment: Reassurance, encouragement, hope
* For guilt: Absolution, forgiveness, redemption
The best synonym to use will depend on the specific situation and what you want to convey.