"I was particularly touched by the lovely personal notes from Harry Connick Jr. and Katie Couric, who are two of my favorite people," Cassidy told People on Wednesday, adding that his former Partridge Family co-star, Danny Bonaduce, also contacted him to "offer kind words, encouragement and support."
"To the many thousands of people who have supported me over the last 5 decades I send my love. I thank you all sincerely for the support and care you have shown me recently and in the past," the singer wrote.
"Thank you for the many letters and messages of concern and care," he continued. "I have my good days and very occasionally a bad day."
Cassidy also updated his fans on what he's been doing since he decided to retire from touring, writing, "I am enjoying some time at home, appreciating the warmth and contemplating what I will be doing next."
The 66-year-old artist also explained that, while he doesn't want to tour any more, he's still devoted to making music.