why does the fitted model give good result on testing but terrible result when doing predict on training

[ramdhan1989]

Hi,
I am just wondering after playing around with the package using my own dataset. I split the data into training and the last 180 data as testing dataset. The fitted model gives good result compared to testing data but when applying predict procedure back to the training data the result is terrible. Is it normal? or am I doing a mistake?
Please advice,

Thank you