It's the comparison between being a grandparent, and being a parent -
The candidate is a grandparent - "You want chocolate? Sure, eat chocolate! You want to climb trees? No problem, climb away! You want to stay up well past bedtime? Sure, stay up with me and we'll watch TV together."
As a grandparent, you can provide all the indulgence you want, and be thought of as wonderful because you do, and that is your role.
The president is a parent - "No, you can't do those things because I have the job of showing you how the world works, which includes not having everything you want just because you want it. We have to think of other people, and talk things over, and that's the way it is."
As a parent you have to make unpopular decisions because it's the best thing in the long run. You have to provide all the difficult decisions and chjoices and be thought of as a pain because you do, and that is your role.