It would help if you share a Post Mortem with us, so we can see how you manage your inventory and what traits you choose.
But generally the best tips i can give are:
Start exploring a level around the edges, and work your way to the center making sure there's no enemies at your back.
Expect the worst that can happen in any given situation and anticipate that.
When in doubt, stop for a minute and think about how to continue best.
Keep a versatile weapon arsenal.
Dont pull levers unless you are certain you can deal with any negative effects.
And finally: Fear Cacodemons!!
