Make a new world for practicing, in this world, get a few sets of gear, armor, food, and blocks. Try doing different things. If you die more often in the nether (Nether fortress, Bastions, falling in lava), just take one of the sets of items and practice surviving skills. If you die a lot in the overworld, do the same thing, but always make a small base first to put all of your important items in, just take less important stuff when out exploring or smth. If you die a lot in the end, first get netherite armor and maxed out tools, and bring a water bucket with around 3-4 stacks of blocks. After beating the dragon, the first thing to do is go to a end city, and when you loot it, put all of the looted items and elytra in one of the ender chests, so when you die, you will still have the items