No doubt one of the things that can prevent proper khushu is praying when one needs to go to the washroom. The Prophet, peace and blessings of Allaah be upon him, forbade praying when one is suppressing the urge to urinate or defecate. (Reported by Ibn Maajah in his Sunan, no. 617)
If anyone is in this position, they should first go to the bathroom and answer the call of nature, even if they miss some of the congregational prayer, because the Prophet, peace and blessings of Allaah be upon him, said:
“If any one of you needs to go to the toilet, and the prayer has begun, he should go to the toilet first.” (Reported by Abu Dawood, no. 88)
If this happens to a person whilst they are praying, they should stop praying, go and answer the call of nature, purify themselves then pray, because the Prophet, peace and blessings of Allaah be upon him, said:
“There is no prayer when there is food prepared or if one is suppressing the urge to expel waste matter.” (Saheeh Muslim, no. 560)
Without a doubt, trying to suppress an urge such as this takes away khushu. This ruling also applies to suppressing the urge to pass wind.