Risk it\run the risk of are basically the same, though the first would be about a known situation and the second would have to state the danger.
I knew I might get the sack, but I decided to risk it.
I didn't do it because I didn't want to run the risk of losing my job.
take my chances- IMHO, this one is normally used in the positive.
People said I would probably fail, but I decided to take my chances.
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