The best way I’ve found to monitor my own ungrateful heart is to have a complaint-free day. I’ve put a rubber band or an easy-to-remove bracelet on my arm. Then, when I do get ready to complain, I move it from arm to arm.
This points out the problem. Gratitude is the solution. Whenever we are ready to complain or grumble, we need to follow the suggestion/command in 1 Thessalonians 5:18:
In everything give thanks. For this is God’s will for you in Christ Jesus.
Gratitude is also the answer when we are prepared to be proud or boastful about ourselves. It’s not us, after all. God has given us the gifts we have, and He has provided graces to make things possible for us to do.
So try a complaint-free day. Change the band on your arm when you feel you want to complaint and consciously move to gratitude. You may find that it feels so good that you can stretch it into a complaint-free week or more.