You know your...

You use 'you know your...' to let your speaker know you're about to say something funny. By using 'you know,' you are also trying to get the speaker into your corner, so they will relate to you.

Example:
-You know your cell reception is bad when you get a text message 5 hours later!
-Yeah, that's pretty bad!

Let me let you go

'Let me let you go' is used in a phone conversation. The person who says it is trying to sound polite by saying they don't want to take up too much of the other person's time. The reality, though, is that usually the person who says this is simply trying to find a nice way to end the conversation without appearing rude.

Example:
-(slight pause in the conversation)
-Well, let me let you go. I'm sure you have a lot of things to get done today!