Rather than clearing all answers from the survey (which you can learn how to do here), you can delete an individual participant's responses - including your own.
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First, go to your project and select the Participants tab.

From the Participants tab, scroll past the Map Overview and Referral Traffic Sources until you see the Participants section. 

Find the participant whose data you'd like to delete and click the "X" icon in the far right column of the participant's row. This will remove all responses from that individual.

See also:

Recovering archived content in your project

How to delete a question

How to delete a project