The actor - whose eldest child Jett died after suffering a seizure on holiday in the Bahamas in January aged 16 - was astonished by the messages of support he, wife Kelly Preston and daughter Ella, nine, received from well-wishers after the tragedy.
He said: "I just want to take one moment to thank each and every one of you throughout this country, throughout the world for all your support and all your love for our family. Thank you very much."
The `Pulp Fiction` star is throwing himself into a new hobby to help cope with his grief - playing tennis late at night with his staff.
He explained to US talk show host Ellen DeGeneres: "I play at midnight. Kind of vampire style.
"The house manager and the house maintenance person, they both live my hours, so ... at midnight we go to the local tennis court."
Earlier this week, John revealed he and his family have been undergoing daily Scientology counselling to help cope with their grief.
He said: "We`ve been working very hard every day as a family to heal. We have our own way of doing it, and it has been helping."