Just like any mechanised or electric device, garage doors occasionally fail to comply with your desires and have to to be repaired.
If the door is down and won't go up, regardless of your physical efforts or that of your door opener, the trouble is most likely a broken spring.
There are two main kinds of springs in garage doors. There's torsion springs which are mounted above the door opening and tension springs which are mounted along both tracks. Both tension springs and torsion springs serve the identical purpose, they supply much of the power that allows you or your opener to open your door.
If one of these springs is broken it may be difficult or totally impossible for you or your opener to open your door. This characteristic of garage doors is what can turn a enjoyable day into somewhat of a bad day, specially if your car is stuck in your garage and you need to go somewhere, like work.
Unfortunately for most home owners, if one of your springs is broken, there's not much you can do apart from to call a garage door repair company and have them come out and replace the springs.
But here's an item you can and should fix for yourself. If you have an opener, you also have some type of interrupter device that keeps the door from closing if its path is blocked.
Perhaps the most common interrupter device is a set of "eyes" that are mounted on the garage door track. They point to each other using an infrared beam. One is a transmitter and the other a receiver. If the receiver can't receive what the transmitter is sending then the garage door will stop and usually reverse. Often this is accompanied by the garage door opener light flashing.
One cause for your eyes not to work is that they have been bumped in such a way that they no longer point in the right direction. A small adjustment can usually take care of this.
The main cause for this beam to be interrupted is that there is something blocking it. After all, that is why the device is there. Look for and remove the item that is blocking the beam and you're probably good to go.
Another cause for failure is that some dirt or condensation has gotten on the lenses of the eyes and they can no longer complete the circuit.
Fortunately for the homeowner whose garage door has turned into a wall there are companies who specialize in helping. They are fully insured and licensed and can be at your home in short order when you encounter a problem that is beyond your means to fix.