When feeling regret, your mind exists in the mental past. Mentally and visually shift yourself to not the present, but the future where you are stronger, bolder, lively, and in a place of overall well-being.
When feeling fear, your mind is clinging on to the past too. Shift your mind from the past or future to the present where everything is completely fine. Repeat this for several repetitions until you are fully in the present. Fully visualize your mental shift.
When feeling the lack of gratitude or appreciation for something or someone, shift from the present to a past time when you had less, much less. Shift to the time when you didn’t have that “thing” or “someone” that you are taking for granted in the present.