I think it is possible to hold onto a feeling like love or compassion

Exercise 1a: Say the word "goat" out loud a few times.
Result: you can say the word "goat" repeatedly and thereby intentionally hold onto a verbal expression.

Exercise 1b: Say the word "goat" in your head a few times.
Result: you can say the word "goat" repeatedly and thereby intentionally hold onto an internalized expression.

Exercise 2a: Tap your finger on a surface.

Result: you can feel your finger intentionally for an arbitrary duration

Exercise 2b: Feel your finger without moving it or touching anything.

Result: With practice at interoception, you can feel your finger.

The purpose of these four exercises was to demonstrate that it is possible to hold onto a thought and a felt sense. Therefore, it should be reasonable to extend the practice to emotions.

Exercise 3a: Feel love or compassion by situational exposure

Result: you can feel love or compassion

Exercise 3b: Feel love or compassion by without situational stimulus.

Result: you can feel love or compassion