What does the idiom listen to your heart mean?

It means to be aware of your feelings and let them guide you. Your feelings are there for a reason, so what you can do is try to understand them, rather than try to suppress them.

Often we tend to make decisions based on what our logic (ie. our brain) tells us to do. But not everything in life is logical, and so to listen to your heart is about listening to your needs. When you feel something in your heart, there is a message there. Sometimes this is in the form of a gut feeling or a hunch.

Listening to your heart can be most important when you need to make important life decisions where logic is not the issue, but where your own happiness is at stake.