I feel empty inside
What makes you feel empty?
A deep sadness still dwells in my heart
It is understandable if you have memories that deeply impact you. You should talk to someone you trust if the feeling of emptiness happens often.
I'm not a crier. It's the only feeling that I can't hide behind indifference
I wouldn't hurt to talk about your feelings with someone close. You should try to get professional help if you don't trust anyone.