“Who do you let in?”

Tessa Gray, to Clary Fray, pg. 716
Source: The Mortal Instruments, City of Heavenly Fire (2014)
Context: I feel a kinship with you, too, you who have lost both brother and father. I know you have been judged and spoken of as the daughter of Valentine Morgenstern, and now the sister of Jonathan. There will always be those who want to tell you who you are based on your name or the blood in your veins. Do not let people decide who you are. Decide for yourself. That freedom is not a gift; it is a birthright. I hope that you and Jace will use it.

Source: Bloodlines

Variant: Love who you love while you have them. That's all you can do. Let them go when you must. If you know how to love, you'll never run out.
Source: My Name Is Memory

Review http://www.rogerebert.com/reviews/resident-evil-apocalypse-2004 of Resident Evil: Apocalypse (10 September 2004)
Reviews, Half-star reviews

Source: The Fountainhead

Source: East of Eden

Originates in a 2007 blog post by Iain S. Thomas entitled The Fur http://www.iwrotethisforyou.me/2007/08/fur.html
Misattributed

Original: Lasciatevi influenzare dalla vostra mente, non dalle menti di coloro che lo fanno per lavoro.
Source: prevale.net