Having a sutrah, or barrier in front of you when you pray, and praying close to it, will help you develop your khushu. This is because it restricts your field of vision, protecting you from the shaytan and keeping people from passing in front of you, which causes a distraction and reduces the reward of the prayer.
The Prophet, peace and blessings of Allah be upon him, said:
“When any one of you prays, let him pray facing a sutrah, and let him get close to it.” (Recorded in Abu Dawud no.695 1/446)
Getting close to the sutrah is very beneficial, as the Prophet, peace and blessing of Allah be upon him, said:
“When any one of you prays facing a sutrah, let him get close to that so that the shaytan cannot interrupt his prayer.” (Recorded by Abu Dawud no.695 1/446)
The Sunnah in getting close to the sutrah is to have three cubits between it and the spot where one prostrates, or to allow enough space for a sheep to pass between the two, as is reported in al-Bukhari.
The Prophet, peace and blessings be upon him, advised the one who was praying not to allow anyone to pass between him and his sutrah. He peace and blessings of Allah be upon him, said:
“When anyone of you is praying, he should not allow anyone to pass in front of him, and he should prevent them as most as he can. If he insists, he should fight him, for he has a companion [i.e. shaytan] with him.” (Recorded in Muslim 1/260)
Imam An-Nawawi, may Allah have mercy on him, said:
“The wisdom in using a sutrah is to lower your gaze and not look beyond it, to prevent anyone from passing in front of you… and to prevent the shaytan from passing in front of you and trying to corrupt your prayer.” (Sharh Sahih Muslim 4/216)