Merging with a bf when hanging out together

I’ve been working on my thoughts about my relationship with my bf and yet I still notice a merge (and by merge I mean fully focused on us and not hearing my own voice very well).  It’s harder for me to set boundaries because I’m not sure I want them when we hang out for a long time together. I enjoy it but once he is gone it’s hard for me to get back to my routine.

I’ve been asking myself in what ways am I not merging with him? And I have a few examples (which usually happens in the beginning of our hangouts). The longer hours/days we hang out, the stronger the merge.  When I am left on my own it takes me some time before I can fully come back to reality and understand what I’m doing.  So how can I stay strong in me when hanging out with him?  Is it all about the thoughts I’m thinking?  Thank you.