"We are always where we (choose) to be."
Each of us (chooses) our own friends, lovers, and spouse.
The beautiful thing about a door is it lets those who want in (in) and those who want out (out). No one is "stuck" with anyone.
Therefore if someone is unhappy with the love life they have with someone and they continue to stay with that person then they are (choosing) to be unhappy. "We are always where we (choose) to be."
Essentially what the character is saying in the movie and in life is if we (really) are unhappy we will make changes. While it is possible for someone to think, feel, and say they're "unhappy" it's their (action or lack of action) that lets you know just how unhappy they really are.
Ultimately what many people call "settling" is actually a person weighing out their options along with the possible (cost versus reward) for a thing they want and then making a final decision. In other words we choose what we think is our BEST option based upon how much effort we're willing to exert to get what we want.
If you want something different you have to do something different.