I think it is very good that you tried to stop complaining for one day. I liked how you use gratitude to shift your focus from complain to something more positive.

1 solution I have to stop complaining is you can make up ridiculous reasons when you have a complain. For example, I have a headache because I am wearing black socks. By saying something so, you interrupt the negative pattern in your mind and thus, you will not stay negative. This is one of the Little Voice methods I learnt from Blair Singer.

I hope it helps.