Grumble: to complain somewhat pointlessly; to mutter on sullenly, to speak out of unhappiness and discontent. Grumbling is the exact opposite of gratitude and praise.
But Jesus, conscious that His disciples grumbled at this, said to them, "Does this cause you to stumble?" John 6:61
"Do not grumble against one another, brothers, so that you may not be judged; behold, the Judge is standing at the door." James 5:9
"We must not indulge in sexual immorality as some of them did, and twenty-three thousand fell in a single day. We must not put Christ to the test, as some of them did and were destroyed by serpents, nor grumble, as some of them did and were destroyed by the Destroyer. Now these things happened to them as an example, but they were written down for our instruction, on whom the ends of the ages has come." 1 Corinthians 10:8-11
"Do all things without grumbling or questioning, that you may be blameless and innocent, children of God without blemish in the midst of a crooked and twisted generation, among whom you shine as lights in the world, holding fast to the word of life, so that in the day of Christ I may be proud that I did not run in vain or labor in vain." Philippians 2:14-16
Instead of grumbling, try gratitude.
Cultivate a thankful heart. Write a letter to someone you appreciate. Tell them how grateful you are for what they have done for you. Sing a song of praise to God. Make a list of your blessings. Tell others how blessed you are. You'll keep yourself from stumbling.