あまり

As mentioned earlier, あまり means “excess”. It can be used with nouns to describe an excess of something. Since あまり is an adverb, there must be something after the あまり for it to modify.

There are a few different patterns with this, but all of them have basically the same meaning.

Noun + のあまり

Because of Excess Noun
Noun + のあまり

This pattern literally means “Excess of Noun”. It is used to express “too much X”.
It is typically used with Emotion words.

Examples

• 嬉しさのあまりで…
  Excessive happiness…(Sentence is incomplete)
  
  
• 涙のあまり、前が見えない
  Because of excess tears, I couldn’t see in front of me.
  
  
• 心配のあまりに、寝られなかった
  Due to worrying too much, I couldn’t sleep. 
  
  

あまりのNounに/で

Because of Excessive Noun
あまりの + Noun + に/で

You can also reverse the order and put あまり in front. This pattern must have a noun after it. 
Another crucial thing to be careful of with this pattern is that the に/で must go directly after the noun.
Do not add a verb before the に・で

Examples

• あまりの心配で寝られなかった
  Couldn’t sleep due to excess worrying. 
  
  
• あまりの痛みに声を出した
  Let out a voice at the excessive pain
  
  
• あまりの悲劇に泣いた
  Cried at the excessive tragedy.
  
  

あまりに

Because of excessive Xing
Plain form verb + あまりに
あまりに + Verb/Adjective + ので/から

Similar to あまりの with nouns, あまりに can be modified by verbs and used to modify verbs or adjectives.

Verb + あまりに

• 勉強するあまりに、寝るのを忘れた
  Because of too much studying, I forgot to sleep.
  
  
• 心配するあまりに、よるは寝られない
  Because of too much worrying, I can’t sleep at night
  
  
• 頑張ったあまりに、ひどく疲れている
  Because of having tried too much, I’m horribly tired.
  
  

あまりに + Verb/Adjective

The ので/から is required.

• あまりに食べたから、いたい
  I ate excessively so it hurts now.
  
  
• あまりに寝たから、体がいたい
  I slept too much, so my body hurts.
  
  
• あまりに嬉しいから、笑っている
  I’m laughing because I’m too happy.
  
  

A note about に

Since あまり itself is an adverb, に in あまりに is omittable when:

• it comes after のあまり
• Verb + あまりに

It is not omittable later in the sentence when used with あまりの (Unless で is used instead)

Additional Reading

This was an annoying one to write, and I’ll probably try to rewrite it in the future.
Here’s some additional readings on this grammar point:

Edewakaru (Japanese)
Japanese Bank (A lot of Japanese)
Takoboto (English and short)