You can do it only in your mind, and you can also keep a diary or take notes to do it.

你可以只在脑子里完成，也可以写日记或做笔记。

youdao

Dear teacher, not only in your mind today, but today, miss you!

敬爱的老师，并不是只在今天才想起您，而是今天特别想念您！

youdao

They must be written, as those kept only in your mind have an uncanny way of remaining figments of your imagination.

它们必须写下来，因为那些只保存在脑子里的目标会神不知鬼不觉的成为你想象中的臆造物。

youdao

And so you know that if only you were to read these things in the envelope, you would change your mind and no longer want to go out with her.

所以你知道,只要你看了信封里的内容，你会改变主意,不再想和她约会。

耶鲁公开课 - 死亡课程节选

Only in your deranged mind is a money bill not to be questioned.

FORBES: James O'Keefe Pays $100,000 To ACORN Employee He Smeared-Conservative Media Yawns

You have the chance to create something that only exists in your mind, or recreate something that exists, but more efficiently, more profitably.

FORBES: The Disconnect

You could reinvent yourself, if only in your own mind.

ECONOMIST: Being foreign