What is it like to know two languages?

To all multilingual ones here, I pose this question: what is it like knowing multiple languages? Do you think in different languages, change when the environment does, or switch between them randomly? Do you ever get your words mixed up (i.e., you're talking to an English speaker but instead of saying cheese you say queso)? Do you find that knowing another language helps or hinders your understanding of your native one?

Pick and choose whatever you want to answer, but thank you for your time either way!

>>21
You seem to be confusing some things. Thinking in a language does not mean saying words out loud. Thoughts are abstract, a child learns the means of putting out those thoughts at the ages of 4 or 5 onwards. That's when we start using our native tongue, and that's what those of us who said "we think in multiple languages" were referring to. If you don't do it like that, you're no more talented than an autistic person (as >21 pointed out), because you have no means of outputting your thoughts.