All of us, of course, have an ego; but I'm not sure I'd agree that all of us have to deal with an inflated or over-indulgent one. There are people who have perfectly healthy egos that they don't inflate or over-indulge their own.
My suggestion to anyone who at least has enough control over his ego to notice that it sometimes gets inflated (and not everyone with an inflated ego even recognizes it in himself) would be to keep in mind that an inflated ego is like an inflated ballon: It doesn't take much for someone else to come along, use a very tiny pin to burst it, and leave nothing but flatted bits in its place. And, keep in mind that it takes a never ending supply of "hot air" to keep inflating yet more balloons.
Better to build one's identity, self-esteem, and sense of self on something of a lot more substance than that.
OR, maybe it's easiest to do this if someone else is around at the time the ego is getting out of control: People should ask themselves if they had to assign a "Number 1" and "Number 2" to themselves and someone else (it doesn't matter how many others there are). If inflated ego person automatically knows he'd assign a "Number 1" to himself and a "Number 2" (with the number representing "importance as a person" or "superiority as a person") to others; he should tell himself what his mother may never have told him, and that's that no matter how "wonderful" he is in one way or another (or all ways), there's a whole lot of other people equally, or even more, "wonderful" in those ways.
The person with a slightly out-of-control ego problem will probably keep his own ego in check if he thinks of that. The person with a real ego problem won't be able to convince himself that those others just might deserve the "Number 1" more than he does. Personally, I think the person who has trouble imagining that he might not always be Number 1 in "importance" or "general superiority" should get counseling, because an ego problem to that extent can destroy relationships.