These things happen. But that doesn't mean you have to accept it without a fight. Regulation (EC) 261/2004 concerns your rights when traveling by air and regulates compensation for passengers for delays, cancellations, or denied boarding. Compensation is usually calculated based on the distance of your flight and the length of the delay.
You can get up to €600 in compensation for flight delays of over three hours. Something is better than nothing, right?
When you miss a connecting flight, your rights depend on the airline you fly with, the country you are flying to, and also the country of origin of the same airline. But don't worry, if you've reached your final destination with a delay of more than three hours and your flights are under the same reservation, you are covered by Regulation (EC) 261/2004, so you are entitled to compensation.
The best way to check is through Wings to Claim.
Sometimes, airlines deny boarding to passengers due to overbooking or airline management issues. If you find yourself in that situation, they must rebook you on another flight and offer compensation for the air incident.
Wings to Claim will get it for you.