Promise - vase
Secrets - glue
Telling secrets often - putting flowers inside once a week
Broken vase - broken promise
Me still putting flowers inside - me still telling secrets = useless.
It's like this:
You and your friend make a vase for art class. Your job is to each dab the vase in glue, since it has some cracks and pieces, every week. You and your friend put glue alternately, and it works for a while. Then your friend stops putting glue. The vase needed it; it broke from the lack. You trying to keep adding glue is useless; the vase is already broken.
Meaning: You and you friend make a promise. Each of you has to tell each other if anything occurs, or if there are any new secrets. Both of you share secrets for a while and it's great. Then your friend stops telling you things, even after the promise was made. That's what the promise was all about. Without the secrets, the promise means nothing. Telling your friend more secrets is pointless; the promise is already broken. Therefore you don't need to say anything anymore.