make a clean break
A complete removal from a (usually negative) situation, relationship, or attachment, with no intention of returning. After spending years in an emotionally abusive relationship, Patrick finally decided to make a clean break and leave his girlfriend.
make a clean break (from/with someone or something)
To remove oneself wholly and permanently from a relationship, situation, or attachment. I've been lingering too much on the mistakes I made in the past. It's high time I made a clean break and started fresh! The esteemed scientist, having made a clean break with her former university, has set up a new research firm in Silicon Valley. I think I need to make a clean break from Robert. Our relationship has just grown so co-dependent lately.