The striker failed to register against Kilmarnock, Hearts and Dundee during a mini drought and the doubters opened fire on the attack-leader.
Griffiths said: “It was a wee barren spell, but it was the first one I have had all season.
“Actually, I would quite like to thank the people who took a real pop at me because I am determined to show them that I am not finished yet.
“I heard one pundit on the radio saying that my season was over, that I had hit the wall.
“Well, I have no intention of stopping before the season is over. There are five league games left and the potential of two Cup games.
“I have more goals in me. It would be nice to get to 40. I think that would be an amazing return for the season, but the most important thing is that we win the league and the Scottish Cup.
“Criticism motivates me. My first focus is to play well and create chances that can help my team win the league.
“But we have a team of winners here – we ALL want to win.”
Last season, Griffiths scored with an early header as Ronny Deila’s men cantered to a 2-0 success over their Glasgow rivals in the League Cup semi-final.
The former Livingston, Dundee, Wolves and Hibs attacker admitted: “I didn’t have any idea what to expect the last time we played Rangers (sic), but now it is different.
“If I can score and get us into the Cup Final, then that would be brilliant.
“However, the most important thing about a game like this is not who scores, but to make sure that we get through.
“We know what it means to everyone at the club and it is all about going out there and giving it everything.
“It is nice to be heading into that game having scored a couple at the weekend – although my head was a wee bit down when I missed the penalty.”
Griffiths, though, fired a warning to Mark Warburton’s team as he prepared for Hampden.
He added: “I ALWAYS fancy myself to score. I think I will always have that confidence when I walk onto the pitch.”