Why can't you say utterly excited?
utter - utterly
Utterly doesn't go with excited because if you are excited about something that is normally a positive emotion and both utter and utterly (meaning complete/completely) have negative meanings and are used only in negative contexts:
To say that we'll be landing on Jupiter in 2010 is utter nonsense.
If you think that, then you are a complete and utter fool.
To spend all day window-shopping, especially at Christmas, is an utter waste of time.
They had no means of support and were utterly dependent on their parents.
To suggest that there should be a total ban on smoking is utterly ridiculous.
complete - completely
Complete and completely are much more neutral and can be used in positive, neutral and negative contexts:
Jon has sent me ten red roses and that has come as a complete surprise.
I'm a pessimist and she's an optimist so she's the complete opposite of me.
He has lied to me so there is a complete breakdown of trust between us.
The PM's treatment for an irregular heartbeat has been completely successful.
When I go on holiday next year, I'm looking for something completely different.
Dozens of homes have been completely destroyed in the floods.
However, despite the flexibility of this adjective/adverb, we cannot say completely excited. One of the hallmarks of a proficient language learner is knowing which adverbs collocate with which adjectives. So, which adverbs go best with excited?
terrible - terribly One of the most common adverbs used with excited is terribly. Note that the adjective terrible (meaning horrible, dreadful, awful) can only be used in negative contexts but the adverb terribly can describe extreme behaviour in both negative and positive contexts.:
What's wrong? You look terrible. ~ I'm in terrible pain.
His sudden death came as a terrible shock to the entire family.
Prison life is terrible and I have the most terrible nightmares every night.
The children were terribly upset when their pet dalmation puppy died.
Children in Britain get terribly excited on Christmas morning when they come down to open their presents.
awful - awfully
Note that awful and awfully follow a similar pattern. As an adjective, awful is used only in negative contexts, but as an adverb awfully has both negative and positive meanings:
It's an awful shame that she's unable to come back home for the holidays.
She was late and I was worried that something awful had happened to her.
He was awfully drunk. It was an embarrassment to have him there.
He may get on your nerves, but he has always been awfully nice to me.
She's awfully pretty, don't you think? The most striking person in the room!
It's awfully good of you to find the time to help us with this.
Note that awesome, meaning very impressive and sometimes a little frightening is a favourite adjective used by young people and people in the media currently:
Thierry Henry's ability as a footballer is just awesome.
It was an awesome party. We danced all night and then watched the sun coming up over the sea. No better way to welcome in the New Year.