Watch the forms: himself (never "hisself") and themselves (never "theirselves").
试一试: They enjoyed ___ at the party. (themselves / theirselves / themself) 答案: themselves — 一个人以上的时候，用 themselves。"Theirselves" 是常见的错误说法，但不是真正的单词；"themself" 又漏掉了表示复数的 -selves：they → themselves。
试一试: The dog is clean now. It washed ___. (itself / himself / it) 答案: itself — 狗是一只动物，动作又回到了它自己身上，所以 "it" 对应的 -self 词是 itself。"Himself" 是用于男性的，而 "it" 表现不出动作回到自己身上：the dog washed itself。
试一试: Welcome, everyone! Please help ___ to some food. (yourselves / yourself / yourselfs) 答案: yourselves — 你说话的对象不止一个人（everyone），所以要用复数的 -selves：yourselves。"Yourself" 只指一个人，而 "yourselfs" 不是真正的单词：yourselves。
动作回到自己身上时
如果一个人对自己做了这个动作，就用 -self 系列的词，不用 me / her / them。这个 -self 词就是承受动作的人——做动作的人，也是承受动作的人。
I cut myself while cooking.
She taught herself to paint.
Be careful, don't hurt yourself.
Not "I hurt me." — say "I hurt myself.". 做动作的人和受影响的人是同一个人，所以用 myself，不是 me。
试一试: Be careful with the knife. Don't cut ___. (yourself / you / youself) 答案: yourself — 你是在提醒同一个人别割到自己，所以动作是回到自己身上的：yourself。"You" 会让人以为是别人，"youself" 又少了个 -r：yourself。
We helped ourselves to cake. (us, the same people)
Not "She saw her in the mirror." — say "She saw herself in the mirror.". 在镜子里看到的是自己，所以用 herself。Her 会让人以为是别人。
试一试: Hiroshi looked at ___ in the mirror. (himself / him / his) 答案: himself — 他在镜子里看到的是自己，himself。"Him" 会让人以为是另一个男人，"his" 表示所属关系，不是指人本身：Hiroshi looked at himself。
myself 表示强调
-self 词还可以表示强调：“就是那个人，没有别人”，常常带有没人帮忙的意思。这时它不是承受动作的人——把它去掉，句子照样成立：I made this cake myself → I made this cake.
I made this cake myself. (I did it, no one helped)
The manager herself phoned to say sorry. (the manager, not an assistant)
You can move it to the end: I fixed the bike myself = I myself fixed the bike.
试一试: Nobody helped Sara. She painted the whole room ___. (herself / her / she) 答案: herself — 这里的 herself 表示强调：Sara 是独自完成的，没人帮忙。她粉刷的是 "the whole room"，不是 herself——你甚至可以把这个词去掉（She painted the whole room）。所以表示强调的词是 herself。
试一试: Kenji 给自己的厨房做了一个架子。没有人帮他——所有活都是他一个人干的。 哪一句加上了“他自己做的，没人帮忙”的强调？ (Kenji built the shelf himself. / Kenji hurt himself with the hammer.) 答案: Kenji built the shelf himself. — "Kenji built the shelf himself" 里的 himself 表示强调：他一个人完成了这项工作，他建的东西是 "the shelf"。"Kenji hurt himself" 是另一种用法：那里动作回到自己身上，himself 是受伤的人。这个情境讲的是独自完成，所以：built the shelf himself。