"I remember after we lost Dad, so many adults came up to me and said, 'Honey, time heals all wounds,' " Bindi, who turns 16 on July 24, tells PEOPLE in this week's cover story. "That is the biggest lie you will ever hear. It doesn't."
She continues, "That kind of sadness never goes away. It's like losing a piece of your heart that you never get back."
Speaking in-depth for the first time about her grief, Bindi also shares how she and her mom, Terri, and 10-year-old brother, Robert, have found ways to move forward.
"When you lose a loved one, you come to these crossroads," says the young conservationist, who lives with her family in their home within the gates of Australia Zoo in Queensland. "You can take the path that leads you down the aisle of sadness, or you can say, 'I'm never going to let this person's memory die. I'm going to make sure everything they worked for continues.' "
For Bindi, that has meant carrying on her father's animal-focused legacy, from planning the family's annual crocodile research trip to working with SeaWorld as a youth ambassador.
"Every day is a new journey for me," she says, "and I feel like in my lifetime, I've been blessed to experience such a lot."
Reporting by MONICA RIZZO
For much more from Bindi, her mom Terri and brother Robert, pick up this week's issue of PEOPLE magazine, on newsstands Friday