Another sentence from Kanji in Context:
Those who think highly of themselves and look down on others will eventually themselves be looked down upon (by others).
I've been puzzling over the choice to put は (instead of が) after 自分. It's the only は in the sentence and presumably marks the topic. Actually I find the topic itself unclear, if this was meant as a warning the topic could well be the listener, or this could just be a general observation of people.
What bothers me most is the usage of は in a subordinate clause (of 思う) and nowhere else. Is this a sort of shorthand for not stating the topic explicitly? i.e. could this be reworded as 人は自分が偉いと思って etc?