I haven't tried quite the same thing, but my T has used hypnotherapy and guided visualisations with me, with similar themes - one involved removing rocks from a heavy backpack, another involved throwing pebbles (that represented my negative thoughts) into the sea. The whole process left me feeling a lot more relaxed than I'd been, and, yes 'unburdened'

There are things I've tried in therapy that I've been sceptical of and have made me feel silly... but... sometimes these things are worth a go, in my experience.