Characters frequently say, "may the force be with you." Based on what we learn about midi-chlorians, isn't the force always with you?
These organisms exist in one's body, and they are responsible for one being force sensitive and able to use the force.
They are usually in the same quantity/proportion at all times, I would assume.
Why do characters use this phrase if it doesn't really make sense?
Yes - technically, the Force is a part of all living things, and would therefore always be with someone per se. It cannot be given or taken, at least not with a simple phrase.
Rather, the phrase is a take on a traditional parting such as "God be with you." or "Vaya con Dios" (Spanish for 'Go with God'). Neither of those phrases make much sense, either, considering that most versions of the Christian faith teach that God is always watching over us. But people say it anyway, as a gesture - a way of wishing the departee a safe journey and good luck.
Equivalent phrases might be "Good journey" (I'm looking at you, Masters of the Universe) or "Good luck" - anything that says to the other person "I wish you well while we're apart".
