Tentacles: Enter the Mind

 You can get a revive token four ways. Sometimes during the layers a revive token will randomly spawn, when you complete a layer you will sometimes be awarded with a revive token, occasionally when you crack an egg you will be given a revive token, or you can buy one for 15,000 coins. Once you have one you just need to die and when it gives you the option to revive yourself do it. Most likely you will be using revive tokens in the later layers when trying to pass them so you don't need to go out of your way to get this achievement unless you want it earlier. 

You can get a revive token four ways. Sometimes during the layers a revive token will randomly spawn, when you complete a layer you will sometimes be awarded with a revive token, occasionally when you crack an egg you will be given a revive token, or you can buy one for 15,000 coins. Once you have one you just need to die and when it gives you the option to revive yourself do it. Most likely you will be using revive tokens in the later layers when trying to pass them so you don't need to go out of your way to get this achievement unless you want it earlier.