diff --git a/content/books/things-i-learnt/_index.md b/content/books/things-i-learnt/_index.md
index 75fc820..155d0b2 100644
--- a/content/books/things-i-learnt/_index.md
+++ b/content/books/things-i-learnt/_index.md
@@ -32,6 +32,7 @@ template = "section-contentless.html"
 		* [If You Know How To Handle It, Handle It](handle-it)
 		* [Types Say What Your Data Is](data-types)
 		* [If Your Data Has a Schema, Use a Structure](use-structures)
+		* [Don't Mess With Things Outside Your Project](outside-project)
 * Community/Teams
 	* [A Language Is Much More Than A Language](languages-are-more)
 	* [Understand And Stay Away From Cargo Cult](cargo-cult)
diff --git a/content/books/things-i-learnt/languages-are-more/index.md b/content/books/things-i-learnt/languages-are-more/index.md
index 6133ade..0e3c90a 100644
--- a/content/books/things-i-learnt/languages-are-more/index.md
+++ b/content/books/things-i-learnt/languages-are-more/index.md
@@ -39,4 +39,4 @@ surface of what the whole of a language encapsulates and if you ignore the
 other elements in it, you may find yourself with a cute language in a
 community that is always fighting and never going forward.
 
-{{ chapters(prev_chapter_link="/books/things-i-learnt/use-structures", prev_chapter_title="If Your Data Has a Schema, Use a Structure", next_chapter_link="/books/things-i-learnt/cargo-cult", next_chapter_title="Understand And Stay Away From Cargo Cult") }}
+{{ chapters(prev_chapter_link="/books/things-i-learnt/use-structures", prev_chapter_title="If Your Data Has a Schema, Use a Structure", next_chapter_link="/books/things-i-learnt/outside-project", next_chapter_title="Don't Mess With Things Outside Your Project") }}
diff --git a/content/books/things-i-learnt/outside-project/index.md b/content/books/things-i-learnt/outside-project/index.md
new file mode 100644
index 0000000..7adfddb
--- /dev/null
+++ b/content/books/things-i-learnt/outside-project/index.md
@@ -0,0 +1,35 @@
++++
+title = "Things I Learnt The Hard Way - Don't Mess With Things Outside Your Project"
+date = 2019-06-25
+
+[taxonomies]
+tags = ["en-au", "books", "things i learnt", "frameworks"]
++++
+
+Simple rule: Is the code yours or from your team? Good, go break it. Does it
+come from outside? DON'T. TOUCH. IT.
+
+<!-- more -->
+
+Sometimes people are tempted to, instead of using the proper extension tools,
+change external libraries/frameworks -- for example, making changes directly
+into WordPress or Django. Believe me, I've seen my fair share of this kind of
+stuff going around.
+
+This is an easy way to make the project -- the team project, that is --
+a huge security problem.  As soon as a new version is released, you'll -- or,
+better yet, someone who was not the person who decided to mess with outside
+code -- have to keep up your changes in sync with the main project and, pretty
+soon, you'll find that the changes don't apply anymore and you'll leave the
+external project in an old version, full of security bugs.
+
+Not only you'd end up with something that may very soon put at risk your whole
+infrastructure, you won't take any benefits from things in the new versions,
+'cause hey, you're stuck in the broken version!
+
+Sometimes doing it so is faster and cheaper, and if you would do the same
+thing using extensions or actually coding around the problem, even duplicating
+the framework functions, would probably take longer and make you write more
+code, but in the long run, it's worth the time.
+
+{{ chapters(prev_chapter_link="/books/things-i-learnt/use-structures", prev_chapter_title="If Your Data Has a Schema, Use a Structure", next_chapter_link="/books/things-i-learnt/languages-are-more", next_chapter_title="A Language Is Much More Than A Language") }}
diff --git a/content/books/things-i-learnt/use-structures/index.md b/content/books/things-i-learnt/use-structures/index.md
index 5883d21..c0ed963 100644
--- a/content/books/things-i-learnt/use-structures/index.md
+++ b/content/books/things-i-learnt/use-structures/index.md
@@ -55,4 +55,18 @@ every time.
 So: You data has a schema? Use a Data Class or Class or Struct. Only if it is
 schemaless, then you can use a tuple.
 
-{{ chapters(prev_chapter_link="/books/things-i-learnt/data-types", prev_chapter_title="Types Say What Your Data Is", next_chapter_link="/books/things-i-learnt/languages-are-more", next_chapter_title="A Language Is Much More Than A Language") }}
+I've seen this used at least once. Sure, at the very start of the project, it
+may seem easier to just store the data as a tuple and destructure it and build
+it again when needed. There was even a whole module designed to receiving
+tuples, destructure them and rebuild new ones (for example, a function that
+would receive two tuples and compute the sum of the "value" field of each,
+building a new tuple as a result). But because of this design, to add just a
+new field, I had to change 14 files and do 168 changes around -- 'cause, sure,
+there was a function to add two tuples, but there were points where you need
+just one field, and there wasn't a function for it.
+
+It would be easier to use if there were functions to extract each field, and
+add two tuples, and what else was needed for managing the tuples, but then you
+have to ask yourself: Why not use a class for that?
+
+{{ chapters(prev_chapter_link="/books/things-i-learnt/data-types", prev_chapter_title="Types Say What Your Data Is", next_chapter_link="/books/things-i-learnt/outside-project", next_chapter_title="Don't Mess With Things Outside Your Project") }}