This goes with the posts from the 9th and 10th.
My children have learned not to say they are bored. If they are young, I will try to help them find things to do by listing options. If they can't settle on something, I say, "OK. Since you can't think of anything to do on your own, I thought of something I need you to do for me. You can sweep the floor and while you do it, see if you can think of something more interesting to do with your time after you finish. If not, I can help you find something else to do." They have to finish the task I give them before they can go do whatever they find more interesting. Once usually fixes it, but a few have needed reminders off and on.
For older children who complain once in a great while, I will encourage with words. Sometimes lives are out of balance. We are tired or stressed and need to rest or work in some fun. Routine wears us down. Sometimes we need exposure to new things. I evaluate those things and advise accordingly.
A continually complaining child will be told to help me do my chores. As they work beside me, we discuss other things they find more interesting to do than to shovel rabbit poo for transport to the garden. They have to finish helping me. This teaches them to see a task to completion. I also share:
"A bored person is a sign of a dull mind. God expects you to apply your intelligence to all areas of your life. Whatever task you are doing, you can make more interesting by applying your heart and your mind to it. You will find each role in your life as interesting as you make it. Realize the impact of the work you are doing, and you will appreciate the ability to do it. Your humility is also required. We should never think a task is below us, or we are too intelligent to do something. Jesus, Son of God, washed dirty feet. We are here to serve. A good and faithful servant will give thanks for his task and will also find joy in simply being able to serve. He will make those tasks more interesting and meaningful to himself as he takes joy in doing them."
I often couple this advice with examples of people who would love the chance to do some of the things my child finds "boring." We know many who are sick or face severe limitations.
If I catch myself complaining, I often correct myself out loud where they can hear. Children emulate their parents, so be careful of the example you give. If you will openly correct them, you should openly correct yourself in front of them. A child will respect an honest and humble parent.