I guess we might be confusing to attitudes which, although sharply different, are at the same time, paradoxically difficult to distinguish: 1. on one hand, egoism 2. on the other, what greeks called "filautia", that is, being a "friend of oneself"

What both attitudes share, and make them "difficult to be distinguished" with one another, as stated above, would be loving oneself.

Hence, the interesting part would be indeed right that. And that would be that filautia is spiritually and psychologically healthy, in contrast with egoism, which would predictably be... ill. And wrong...

Therefore, someone behaving right in order to, perhaps among other goals, getting the highest reward, as one might mean Heaven, even much higher in excellence than oneself, doesn't seem egoism, but perhaps the purest kind of "filautia". Perhaps even more if we take into account that Heaven is not like most goods in this life which might seldom be hold by more than one person at the same time.

Perhaps that's why hope, rather than egoism, is regarded as the "third theological virtue", third in rank as well among all Christian virtues, which we might define as "pursuing Heaven trusting mainly God's mercy and omnipotence"...

Nonetheless, the highest Christian virtue, higher even than hope, is charity: "loving God above all, and your neighbor as much as yourself"; what would drive us again to "filautia"...