When it boils down to it a lot of the questions I'm asked require a "Yes." or "No." answer. Usually when the answer ends up being "Yes." it means that I am required to involve myself. "Yes, you may go outside." means that I have to get the kids ready to go out and then take care of all the coats, mittens, etc when they come back in. "Yes, you may play with play-doh." results in me finding said play-doh and also cleaning up the play-doh mess afterward, while keeping the baby from eating the stray chunks that have rolled helter skelter around the kitchen. "Yes, you may play with puzzles." generally means a massive puzzle mishmash occurs in my family room necessitating direction in cleaning up said puzzle wreckage.
It all comes down to what I want to model in this house. These four little people who depend on me day in and day out look to me as their guide. They are regularly taking mental notes on what I do, how I act, and what I say. When I say "No." out of convenience for myself, they're getting schooled in selfishness. When I say "Yes." and put my own needs aside in order to do something for them, or someone else for that matter they get a front row seat to a show of sacrifice. I have the unique opportunity as their parent to daily lay down my own needs in order to meet theirs.
Saying, "Yes." also provides your children with some control, which in turn produces confidence. If I'm always shutting my kids down by saying, "No." to their requests they will have a much harder time making their own decisions. If they feel like their desires are an inconvenience, silly, or unimportant it could be a real detriment to their feelings of self worth.
There will be many unavoidable and necessary "Nos." "No, you may not hit your sister, run with that knife, eat right before dinner, go to that frat party..." I trust that if instead of saying "No." all the time to my kids over inconsequential things and rather taking the opportunity to say "Yes." as often as I possibly can it will breed confidence. They will be more confident in their own decisions. They will be confident that they are loved. They will be confident that when they do receive a "No." that it is for their own well being.
When God sent Jesus to die on the cross Jesus didn't want to, but He said "Yes." for us, because that's how much he loves us. Saying "Yes." to my kids whenever possible is one of the ways that I can not only show them how much I love them, but more importantly how much Jesus loves them.