"There is no going back. All I can do now is apologise and move forward, and hopefully learn to use these challenging times as an example and lesson in the future, and call myself out. Because God knows I went the wrong way for far too long this time around," he began his lengthy post.
The actor said this was the first time he'd had the courage to share this part of his life with the public since the pair's separation in 2017. He said he was having a hard time completely letting go of Lerato and what they had, and that nothing he did helped ease the pain.
"I have never said this in public before but letting go of someone that you love and shared your life with is not an easy road to travel. Everyday feels like the journey just began and will not end. No amount of alcohol, late nights out and different girls can make the feeling of emptiness.
"I have tried and in these trying times I have made one mistake after another, and I have been so stubborn or too egotistical to admit that it is nobody else’s fault but my own. I have blamed everybody but myself and I am extremely sorry that it took this long for me to see."
Siya also used the opportunity to thank Lerato for being a good mother in his "absence".
Click on the post below to read the rest of his message on Instagram.