Resources gained from destroyed enemy

[Suicide Junkie]

You shouldn't have been running your maintenance costs that high, I'd say.
Once your maintenance costs are within a system or two worth of your production, you need to start mothballing all of the new ships you build (reserves) and retire some old ships, or switch over to producing maintenance free units such as fighters.

If you lose a system, it would at worst cause some spaceyards to halt, rather than losing ships.