The Glee actress was shattered when her partner and co-star Cory was found dead in a Vancouver, Canada hotel room in July 2013.
A coroner's report later concluded 31-year-old Corey had died from an accidental overdose of alcohol and heroin.
Speaking in the new issue of Teen Vogue magazine, Lea reflects: "I somehow feel the insane love Cory and I had for each other morphed into this strength that I have right now.
"There's just something about knowing he's watching everything I'm doing and feeling like I have to do everything now not just for me but for him. I also have a safety net below me — if I fall or if it's too much, my friends and family will be there to catch me."
Lea was interviewed by Glee co-star and close friend Jonathan Groff, who has been by her side during the difficult last few months.
Brunette Lea threw herself back into work following Cory's death, both on Glee and her debut album Louder.
The 27-year-old previously said that "going to work is no harder than being at home" and she felt safe on the Glee set, surrounded by others who loved Cory and understood what she was going through.
Lea's debut album Louder is released on 4 March, and looks like it will be a bittersweet experience for the star, as Cory was so proud of the project and wanted to be by her side as she took on the pop world, joining her on tour and supporting her all the way.
"He was such a fan, you don't understand," she said. "He heard every song and gave me his notes on everything."
Lea's full interview is available in the March issue of Teen Vogue, available 4 February.