自己を過信してはいけない。

self; oneself

indicates direct object of action; indicates subject of causative expression; indicates an area traversed; indicates time (period) over which action takes place; indicates point of departure or separation of action; indicates object of desire, like, hate, etc.

trusting too much; overestimating ability

if ... then; when; and; why don't you...?; the more (one does something); because; since