How do you know or trust that your feelings aren't just because you are splitting on someone?

I'm feeling such intense emotions right now about my SO. 
Things feel different to me but he says it feels the same normal split but longer.

So how do you know if what you're feeling is real or the split?
How do you know if the thoughts or worries you have are genuine?

How do you make decisions that are right instead of acting and regretting it later?