Regulation (EC) No 261/2004 of the European Parliament and of the Council of 11 February 2004 establishing common rules on compensation and assistance to passengers in the event of denied boarding and of cancellation or long delay of flights
When you fail to board a flight at the point of origination you are the party in breach of contract. The airline hasn't denied you boarding. If you are denied boarding because the airline has (for example) oversold the flight, then you can rely on the regulation. Similarly if the flight is cancelled or subject to a long delay, you can rely on the regulation. If on the other hand you purchase a ticket and fail to comply with the contract then it is you who are in breach of contract, and nothing within the sections you have quoted (or indeed any other part of this regulation) would appear to protect you for a contract that doesn't exist.