Take a comfortable seat and close your eyes. Notice the subtle pull of gravity on your body, grounding you into your seat. Allow your body to settle.
Your breath may naturally begin to deepen. As it does, try to let your inhales fill your abdomen and lift your heart. Even as you exhale completely, see if you can maintain a sensation of lift and flotation around your heart space. You can even imagine your heart buoyantly floating on water, cradled by your breath. Continue this breath and awareness for a full minute, or more.
Next time your heart is heavy or has a sinking sensation… try this meditation again. And, always know that your breath is your own, personal floatation device.