Djokovic has seen his form dip since crashing out in the third round of Wimbledon last year to Sam Querrey.
In his most recent grand slam -- the 2017 Australian Open -- he was defeated by Denis Istomin of Uzbekistan in the second round.
"If I could describe my tennis in one word, I feel like I'm in transition," Djokovic told the ATP World Tour website.
"From the beginning of my career, I have been very fortunate to experience only an upwards direction in my success and results. After winning Roland Garros [to complete a career grand slam], I didn't know how I was going to feel.
"I never had that issue after winning a big trophy, of bouncing back and finding new ways to motivate and inspire myself. That is, to keep playing at that level and stay emotionally recharged.
"But last year I found some emptiness for the first time in my life in terms of motivation. I needed a few months to think about things and get that mojo back on the court."
The Serbian will next face British No. 3 Aljaz Bedene in the second round of the Internazionali BNL d'Italia in Rome, as he tries to pick up some form on the clay-courts before the French Open begins on May 22.
Djokovic, who is the defending champion at Roland Garros, is bidding to extend a streak of four consecutive seasons with at least one clay-court Masters 1000 crown.
Bedene and Djokovic have locked horns at the Australian Open and Roland Garros over the past two years, with Djokovic winning 6-3, 6-2, 6-4 in 2015 and 6-2, 6-3, 6-3 in 2016 respectively.
"Whatever the future holds, I cannot predict it," added Djokovic. "There are no guarantees. But that's how the life cycle is and I just try to be the best version of myself every day."
Information from the Press Association contributed to this report.