When you vote in person, an election worker at your polling place confirms your identity and verifies that you are registered and eligible to vote. Once you go into the voting booth, however, your ballot is secret--it is no longer associated with your name.
Similarly, processing of mail-in ballots involves confirming the identity the voter, verifying their information to confirm that they are registered and eligible to vote, and checking the signature on the ballot envelope against a signature on file. After confirming this information — which is usually written or printed on an outer envelope — the envelope is opened and separated from the ballot, which protects the voter's right to cast a secret ballot.
This is why you cannot find a history of how you voted in each election; your vote is never associated with your name.