This is something I have thought on a lot. And I do have painfully tended essays in my drafts that will never see the light of day.
However, sometimes I think it's okay to just let it go and let it flow. If that's what we are feeling and the articulation is there, why the heck not? It's as much about being true to ourselves as writers as it is about using what we have in the moment to keep writing and practising our writing.
It's a double-edged sword. When we are consumed with feelings that we write but never finish or publish, we aren't giving ourselves the space we need as writers to grow and improve. Perfection doesn't exist but we continue to strive for it and, in doing so, we can grow our skills. Yet we can never improve by keeping our imperfections private.