It’s called a chameleon circuit. The Tardis is meant to disguise itself wherever it lands, like if this was Ancient Rome, it’d be a statue on a plinth or something. But I landed in the 1960s, it disguised itself as a police box, and the circuit got stuck.
You take the work home with you. If you spend the day replicating what it feels like for your children to die, for example, it’s like you’re playing with your chemistry set, so there’s going to be a little bit of backwash. I go for a run. And drink red wine. Sometimes I run down the street drinking red wine!