In the swing. = If things are in the swing, they are progressing well.
I've got a bone to pick with you. = I have some complaint to make against you.
In someone else's shoes = It is difficult to know what another person's life is really like, so we don't know what it is like to be in someone's shoes.
If wishes were horses, beggars would ride. = Wishing for something or wanting it is not the same as getting or having it.
In a jam = If you are in a jam, you are in some trouble.
In the driver's seat = In charge of something or in control of a situation.
I'll cross that road [or bridge] when I come to it. = I'll think about something just when it happens, not in advance.