What Weakens Imaan

In a nutshell
Sins, heedlessness and hidden hypocrisy: what eats away at faith.
From the Qur'an
To be added: verse text, translation, surah and verse number.
From the Sunnah
To be added: hadith text, translation, collection, number and grading.
In simple words
To be written.
Common misunderstandings
To be written.
What to take away
To be written.
References
To be added.
Editor notes (remove before publishing)
Planned anchors, to verify when collecting: Qur'an 83:14, 57:16; Hanzala hadith (Muslim 2750); heart like a lump of flesh (Bukhari 52, Muslim 1599)