The defender explained that he made the decision after injuring his knee against Hoffenheim last month and feared it could be another cruciate ligament tear.
Sule, who has 49 international caps for Germany, has had two previous ACL tears and has been hampered by injuries since making his professional debut at the age of 17.
Speaking on the Spielmacher podcast, Sule said: "What I felt when our doctor did the drawer test (used to check for a possible ligament tear) in the dressing room at Hoffenheim, when he looked at the physio and shook his head, and the physio did it too and didn't feel any resistance either – I went into the shower and cried for 10 minutes.
"In that moment, I really thought it had torn. When I went for the MRI the next day and got the good news (that it wasn't a cruciate ligament tear), it was a thousand percent clear to me that it was over.
"I couldn't imagine anything worse than actually looking forward to the time afterwards – being independent, going on holiday, spending time with my children – only to then have to come to terms with my third cruciate ligament tear."
Dortmund head coach Niko Kovac said that they will use the final training session to check if Süle is fit enough for the final home game of the season against Eintracht Frankfurt.
Niko Kovac oversaw Julian Brandt's final home Bundesliga appearance for Borussia Dortmund on Friday, as he brought his Signal Iduna Park career to a close in a 3-2 win over Eintracht Frankfurt.
Borussia Dortmund secured a second-place finish in the Bundesliga with a dramatic 3-2 victory over Eintracht Frankfurt at the Westfalenstadion, ending a poor run of form.
We take a look at Sunday's Bundesliga action which saw important goals and shifts on the league table, with European football and relegation looming.
Jobe Bellingham has said he planned to stay at Borussia Dortmund for the long term after reflecting on a positive first season in Germany.
