While Morison has received messages of support from his Lions team-mates, he has become a hate figure on Millwall messageboards on the internet as fans vent their anger at his exit.
The player told The Sun: "I am sad to leave Millwall but I don't feel guilty.
"Millwall hadn't had a 20-goal a season striker for 10 years before I reached that amount the season before last when we won promotion from League One.
"I was disappointed not to get 20 goals this season. I got 17 but when I didn't score I was accused of being rubbish and not trying hard enough.
"But that's fans for you, isn't it? They don't know what goes on behind the scenes.
"They didn't know that for the first three months of the season I played with a broken foot.
"And they don't know that my missus had a baby in April and ever since then I've been getting two hours sleep a night!
"I also played the last two months of the season with a bruised heel. When I wasn't playing, I couldn't even put my foot on the floor.
"I don't want sympathy or a pat on the back. I did it because I love playing football.
"Fans have a go when things aren't going well and it's something you have to take on chin."