We can only guess about what's going wrong for you specifically . But I like guessing:
(extremely mild spoilers:)
- A core skill for Nethack is understanding how much danger you're in at any particular moment. Your comment about soldier ants below tells me you've made good progress here. But you need to recognize when you're in danger and how long you have to deal with that problem before you'll react appropriately.
- Nethack's dungeon isn't linear, it branches. (Think of the gnomish mines here, but there are other examples deeper.) When you're getting in over your head in one branch, go back up the stairs and switch to another one.
- When you're in immediate danger, Stop. Look through your inventory, consider your options. Think especially about wands, think about ways to write Elbereth, think about scrolls. Think about ways to use diagonal movement to your advantage to get to an escape, or a more defensible position. You have all the time in the world to think. There may not be a solution, but I've died more than a few times with more than one thing in my inventory that could have saved me.
- You need to be able to identify some things without waiting for a scroll of identify to fall into your lap. Price is the easiest way to identify the scroll of identify itself. It's also straightforward to learn to identify most useful wands: with spoilers or by experimenting. Engraving with the wand will often give you more information than zapping it. A lot of your early I'm In Danger toolkit will come from wands you've identified this way.
Good luck, have fun.
(Intermediate player, a few dozen ascensions 20 years ago.)