Acknowledging Your Emotion: Why is it important?

A couple of days ago, my seven year-old daughter performed in a dance concert. It was her first public performance and we were all very proud of her. She was very excited about it. We know how much she loves to dance.
Her routine was the first performance and we all thought she did rather well and were happy for her. At the end of the concert, my wife presented her with a present, personally wrapped up by her with a beautiful blue coloured wrapper.
To our surprise, my daughter not only did not say thank you to her mother but actually complained about her present. She said she did not like the colour of the wrapper and did not like the present inside it. She was grumpy all the way from the concert hall to our house. This was so unlike her.
The next day, she was still upset. When we invited her out to the shopping complex for a movie, she declined, claiming that she wanted to stay and rest at home.
I knew that something was bothering her and it was not just about the present but I didn’t know what it was. Anyway, the rest of the family went for the movie and had a nice time. Then it struck me that my daughter may have been upset not so much with her present as with herself. Perhaps she had felt that she did not perform as well as she could have. She does have very high expectation of herself and is quite a perfectionist when it comes to her dance.
Once we returned home, my daughter was at the door to greet us. I knew she wanted to talk and took the opportunity to ask her once again why she was upset. I advised her to tell me the real reason why she was upset and when she couldn’t say it, I asked her directly whether she was upset with herself because she thought she did not perform as well as she could have — and she said “yes”.
Once she acknowledged her real feeling, I was able to console her. I told her that we all loved her performance and that it was more important for her to gain experience from her first public performance than to demand a perfect performance from herself.
Then I told her how much her mother has painstakingly chosen a present for her and personally wrapped it up in a beautiful wrapper for her, and that because she had not acknowledged her true feeling to herself and everyone else, she had instead taken out her anger on her mother’s present. In this way, she not only upset herself even more and felt bad about it, she spoilt the occasion for everyone in the family. Perhaps she had reacted unconsciously. We all have this tendency to deny our feelings and lash out at something else instead - children and adults alike - and some poor innocent person unwittingly gets the blame.
I then helped her to realise why it was important that she honestly acknowledge her feelings. The outcome would have been more desirable and the unpleasant feeling would have been resolved much earlier and easier had she been honest about it in the first place. In addition, her mother would not have been hurt by her reaction to her present and she would have had a wonderful day at the movie with us.
By not acknowledging her true feeling, she reacted in a way that created a chain reaction of anger that was directed at everyone in her path and basically created more problems for herself and everyone else. These problems could have been avoided or would not even have existed had she been honest about her feelings from the beginning.
I thought this was an important lesson for her and for everyone, and was glad to have the opportunity to talk to her about it.
P.S. About an hour later after our talk, she came over and whispered a “thank you, daddy” into my ears and I could see that she was back to her normal self again. It was as if a burden has been lifted from her little shoulders.