Another sentence from Kanji in Context:
自分は偉いと思って人を見下しているとそのうち逆に他の人から見下されるようになる。 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?