How to find the thought

I’m having a hard time identifying my thought that is causing my current emotion. I am feeling sad and tearful and I’m not sure why. I woke up this morning with overwhelming sadness and have been tearful all morning. A C of plans falling through led to disappointment did occur last night but my current emotion feels so out of proportion to that C and I feel clean in my thinking that sometimes plans fall through. I’m currently just allowing myself to feel this sadness and experience it but I’d really like to find out the triggering thought. Any suggestions to help me uncover this?