I've used mode since Sims 1, and barely understood what I was doing. Since then, I've learned that there are different flavors: tuning & scripting, wearables, buyables, create-a-Sim, core mods, and more. I've learned which mods are most likely to break your game, and where conflicts might be. I'm still not ready to make my own.
Some of my families, heck yeah, I'm going to cheat, like crazy. Others, I know how to yank the folder entirely, and make the poor and homeless Sims suffer as they were meant to. Other stuff, I really do feel it's an improvement, and should have been there since day 1. I have a mod for custom lot sizes-- have you seen those crazy non-standard bars Late Night has? I have an auto-save mod, and I don't think I could live without it anymore. Ironically, I avoided all Twallan's stuff because of all the conflicts I'd heard about. I'll agree that his stuff is awesome, and I love how he works with everyone to get stuff working, but I've also decided some things are just not for me.
Personally, I can figure out the mods I download. Some people can't even figure out how to download from anything that's not Sims Exchange. Obviously, mods are not for them, and I would never even begin with "how to modify an XML file using s3pe". Who in the what now? Um, just forget it, before you break your game, okay? No, seriously. GAH, I warned you!!! If you need me to come to your house, and hold your hand, and do it for you, you should not be playing with mods. If you can read, and understand the directions, AND explain it to somebody else, you might be ready. If you break your game, and can't even explain what you did, you're not ready for it. No, I can't fix it if you do that. I tried to warn you. (and people think I'm being so mean when I say that, jeez!)
Save, Save As, Backup, and Restore are your friends!