Totally unreasonable and so angry with myself!
Myself and ex have been finished just over a year and it was dreadfully hard at times (when he met someone else etc, didn't last though). Recently we've really found new ground and been getting on really well as friends, just at drop offs and pick ups etc we'd have a coffee together and a chat. It's been really nice to finally be civil and friendly for DDs sake.
Last night we ended up at a party together and the night was great, totally platonic etc but we ended up back at mine and slept together.
I feel such a fool, like I've undone all my hard work of moving on from the situation 
Have i? How do I ensure things swoop right back to normal and that I don't give this a second thought? Sounds so juvenile I know but it's taken so much for me to get back to normal.