"The thing is..."

The missus was able to find out my favorite phrase. She noticed it after overhearing some of my business-calls. I didn't give it much thought until I was replying to an email earlier. I started typing:

The thing is that...

I guess the missus was right. I tried to rephrase my email but I suddenly had writer's block. Just can't think of a phrase to replace it with.

Why? Well, the thing is...