* For health: "A brisk walk in the morning is a great tonic for both body and mind."
* For music: "The pianist played a beautiful tonic chord to end the piece."
* For mood: "The sound of the ocean waves was a tonic for her weary soul."
* For general improvement: "A change of scenery can be a real tonic for anyone feeling stuck in a rut."
Let me know if you'd like to see more examples!