This could be a very dangerous situation. There are many factors at work here. If your springs are old and not adjusted right then they might not be providing enough lift to help the opener, or they could be uneven, pulling one side up more than the other and causing a jam. If your tracks are bent or damaged then you could have an obstruction. If your rollers are bent, old or rusted then they could be binding. If the chain or related hardware on your opener is not lubed or adjusted correctly it could be binding or damaging the main sprocket. Any or all of these things can create a situation that could damage your drive motor or even cause a danger to you or your family. Do you know if the opener will stop if it contacts a person or child, or will it keep going and crush them? Do you know that if someone, or a child gets caught on the door if it will stop so they won't be hung? All new openers, if properly adjusted have protections for these instances. Here is what you do: Pull the little string with the bead to release the door from the opener mechanism. You need to be sure that when you do this that the door won't fall on your head or on someone, or something else if the springs aren't pulling right. A garage door without springs weighs hundreds of pounds so look at the springs first and maybe have a 2x4 brace under the door to stop it from falling 7 feet and crumbling. Assuming you and your door are still in one piece after disconnecting it then you need to test how the door opens and closes without the opener attached. The springs should evenly hold the door from falling shut until it is about half closed (roughly). If they don't then you need to adjust them. For most people this can be extremely dangerous and can easily cause mutilation or death. Also, your springs, if long coils might not have a "keeper" cable running through them to contain them should they fail. If you have a spring in the header above the door then never do it yourself unless you know how to do it. If your springs are fine then check for ease of operation to make sure nothing binds and for damage to any wheels or track hardware. If everything is smooth, and the springs are adjusted so the door doesn't fall from 1/2 or 3/4 open then look at your opener. Usually you set the down stop point first, then the up stop point, then the down and up force settings, if you have them. the down force setting should allow you to grab the door when its going down and it will stop or reverse without pulling your arms off. Otherwise decrease the down force. Also, it needs to reverse if you put a 2x4 on the ground under it as a safety feature. For up force it needs to be able to lift the door but also be able to stop or reverse if you try to hang on it while it is going up. You might need to buy new opener(s) as the new ones have ALL the right safety features and also the right operating and maintenance manuals. Home depot has some decent, inexpensive Stanley openers that I have had good luck with. $99!!! If any of my post scares you or makes you think you can't do it yourself then you might be best off getting a pro to do it for you. These can either be safe or a pain or can even kill you or a child so do not be satisfied with one that malfunctions.