The 26-year-old suffered a double leg break in an FA Cup tie with Blackburn and came on for his first appearance since then on Sunday.
"I am massively relieved to be back," said Mackie. "I've worked so hard for nine months and I have just been in the gym, grinding it out.
"I've been watching a lot of football and, while I like it, I would much prefer to be playing.
"I am delighted to be back now and hopefully I can make an impact for the manager and the lads.
"It was really hard but I am not the first one who has been injured for a long time.
"A lot of lads have had that in their career and it is part of the territory.
"You have to be strong and fortunately I am mentally strong anyway and I've got through it.
"If in doubt, I've just been thinking about getting back and luckily enough I am allowed to do that in the Premier League."