A: I am unable to make out his heart.
B: He is a man who never wears his heart on his sleeve.
A: Yeah, I can sense his reserve, his secrecy, and his self-control.
B: So you should believe his love, too.
A: Do you really think so?
B: Yes. Look at his eyes, everything is clear.
wear one's heart on one's sleeve
Wear one's heart on one's sleeve的意思是“不掩飾自己的感情”“表露自己的感情”。其英文解釋為：open-hearted and out-spoken。
E.g. She was proud of her love and not afraid to wear her heart on her sleeve.
E.g. My daughter seems to have a succession of disastrous love affairs. However, that's what happens when you wear your heart on your sleeve.
E.g. Helen wears her heart on her sleeve. It's easy to see if she is sad or happy.
E.g. You can't tell how she feels. She doesn't wear her heart on her sleeve.
E.g. Can you make out what this means?
E.g. With so many things mixed up it's hard to make out what's what.
E.g. He couldn't quite make out what it was all about.
E.g. They tried to make out the expression on her face.