The next time you encounter someone who is in love, pay close attention to what they say. What do they talk about? They talk incessantly about the person they love. He tells all his friends about how wonderful she is. She says that he's always on her heart. They are speaking from their heart's abundance (Lk 6:45), and their hearts are abundantly full of love for each other.
Now, think about what you say. How often do you speak of Jesus? Is He on your heart much? Do you speak about your favorite movie star or sports team more than you speak of Jesus? That tips you off about what's really in your heart.
If your heart is full of fear, ask God for a deeper love for Him, for "perfect love casts out all fear" (1 Jn 4:18). If your heart is full of the things of the world, ask Jesus to purify your heart so you will have room for Him (see Jn 2:15ff; Mal 3:3). If your heart is hard and closed to Jesus, commit to read His Word often and hear His voice through the Scriptures (Heb 3:7-8).
Keep your hearts full of Jesus by frequently receiving His eucharistic body and His Word at Mass. Then your heart will burn with love for Him (Lk 24:32). "My prayer is that your love [for Jesus] may more and more abound" (Phil 1:9), and that you know and experience the overflowing love He has for you (Eph 3:19). Then Jesus will be your Love (1 Jn 4:8), Life (Jn 14:6), and Joy. When your heart is full of Jesus, you won't be able to help speaking of Jesus (see Acts 4:20). You'll love to talk about Him.