First you need to figure out if..
A. Does the motor care if it is driven when stalled. Many small motors will quite happily stay stalled almost indefinitely especially when attached to a large metal plate. Handling you holding the switch too long would definitely be anon-issue in this case.
B. Does the motor already have a built in mechanism to cut the power when the load exceeds some threshold. This should be fairly obvious when running it. If it does not you should be able to hear it straining and getting warm. If you can't detect it that way, use an ammeter in series with the switch and see what it does.
Options if neither of those are true.
A resettable fuse is one. However, you would only need one, not two. Put it in the positive wire that comes from the battery before the switch.
However, the fuse would need to be a slow one so that it does not open when the start current flows and would ALSO need to have a reset delay so that it does not just flip on and off rapidly.
These devices are not really intended for high usage, they are more designed to do nothing most of their lives and only act under exception conditions. As such, I would not recommend this approach.
You could add a thermal switch attached to the motor body. If it gets hot, it would cut the power to the motor till it cools down again.
Not exactly a great solution, but it is a safe, and simple one that will help protect you if the switch gets stuck in the closed position.
Smart Current Sensing
A better alternative is to use a circuit that monitors the current and detects the motor hitting the bump stops and then shuts off the motor. Once in that state the circuit would remain off till the demand from the switch changes.
Note, again this circuit needs to be smart enough to ignore the large, changing current, that happens when the motor first starts.
Limit switches / sensors
This is more of a mechanical solution with some wiring. Using two switches and diodes, or sensors, you can detect the end points of the actuator motion and disconnect the power from the motor when it reaches the appropriate position. (See image in Janka's Answer.)
Although a simple fix electrically, this method does of course require some tricky mechanics, especially, in an engine environment where grease, oil, and dirt can bung-up the works.
It does however add a nice feature that you get feedback on the current position and can light a warning light when the thing is open/closed.