When you choose to follow your heart the only thing you long for is letting go your own will and living in love where ever this life may take you. Just let the flood carry you away peacefully as if you are floating in the water on your back and the sun is warming your face.
You are doing this in full confidence in God, even though you do not know where the floating water is taking you. If you would know, your will would be in control again.
So following your heart means letting go your own will. Everybody does this on his or her own way. But nobody can follow his heart by achieving things no matter what they may be. If you follow your will you are achieving.
For example when I publish the Saint Francis Papers on a blog and wonder what people might think of it I am not following my heart, but trying to achieve that people like it or catch their attention. The only purpose of publishing should be that it leaves a good feeling in my heart.
Another example is all your life you are wishing to work in Africa and helping people there. When your plans cannot go on for some reason, you are disappointed, angry and frustrated. Apparently you did NOT follow your heart but your will! You wanted to achieve something in Africa.
When you follow your heart you cannot be disappointed, because you trust that whatever happens or where ever you arrive it is all right! Because following your heart is following God and then every destination is GOOD, as He is love.
Following your heart means your complete surrender and total freedom as your (daily) worries are no longer your concern.
>>B1. How to follow your heart