"Don't be too hard on yourself, you goof/dummy/idiot" 可以用来表达这个意思。这个短语的来源可能源于人们常常用 "goof/dummy/idiot" 这样的词来调侃自己或者他人在做事情的时候出现的小错误或者失误。
例句：
"Come on, don't be too hard on yourself. You're only human, after all." (别太苛刻自己，毕竟你也是人嘛。)
"Don't be a dummy, of course you can do it!" (别傻了，当然你能做到。)
"Don't be an idiot, you can totally ace this test if you just study a pttle harder." (别傻了，只要再多复习一点你就能得高分。)
例句：
"Come on, don't be too hard on yourself. You're only human, after all." (别太苛刻自己，毕竟你也是人嘛。)
"Don't be a dummy, of course you can do it!" (别傻了，当然你能做到。)
"Don't be an idiot, you can totally ace this test if you just study a pttle harder." (别傻了，只要再多复习一点你就能得高分。)