yes, they are similar BUT, “look after yourself!” would most likely be used in certain situations like if your friend is in bad health and not doing anything about it you might say to them: “hey, friend, look after yourself, please!” or if you’re saying goodbye to someone you know you won’t see in a while or never again you might say (with A LOT of emotion in your voice): “look after yourself!” i, myself, wouldn’t say that casually to a friend or family member. i would say: “take care!” i mean, you CAN say: “look after yourself!” but you might get an odd look from the person if they are a native english speaker and/or american. 😊 hope that helps and merry christmas!