Emotions at start of 2nd Tri

Kasha
I'm 13w4d with Di/Di twins. I feel fortunate that my symptoms have been manageable so far physically and emotionally. Today I dropped my mom off at the airport after she came for a short visit. I've essentially bawled on and off from the moment she left until several hours later. I feel sad but can't pinpoint any specific reasons. 
As I begin to calm down and relax, I can't help but wonder if this is a new wave of delightfulness to be enjoyed over the next who knows how long. Any moms-to-be find any calming strategies that work well for you?