Power loss, 2001 Honda civic after about 30 minutes driving on hot days?

Strange power loss in 2001 Honda civic after about 30 minutes driving on hot days. After power failure car will only move at about 15mph with high RPM, but is fine once it cools off. During power failure the engine sounds ok. Occasionally its power will fail completely, the car will shudder slightly, stop and all the lights will come on briefly, and if this is the case it can be difficult to start. It has also been losing water with more being lost on hot days, I can't really find the leak so could be head gasket maybe. I would be very grateful for and suggestions.

You are killing your car. Anytime an engine gets so hot it loses performance and shuts itself off you're destroying it. It sounds like you've done this more than once. Keep driving it and eventually it will die for good. If it's losing water without finding a leak it is a head gasket. Sorry to say, but most likely, you've already done serious damage to your engine.

Buy a bus pass and sell this car before it is completely ruined. This Honda Civic, please capitalize the model names of cars, is on death's row and terminal unless a mechanic resolves what ails it. It may have more than 250,000 miles. Sorry but this vehicle is not working properly. It is done. Kaput. Finito. Done for.

Just to clarify it isn't restringing as overheating, even when it looses power.

Also i stop driving when it looses power an rest it until it behaves normal again.