2:45 And seek assistance through patience and prayer, and most surely it is a hard thing except for the humble ones (Khashi'een)
Muslimah made an excellent point about Khushu' it is a form of "entertainment". The "khashi'een" as in the Ayah 2:45 are identified through the ease in which they are able to worship and persevere in Allah.
The question is how does one obtain khushu'?
I mentioned before that cursory look at the word Khushu' in the Quran will show that it is inextricably linked with the quality of Iman. It is always mentioned as a quality of the Mumin.
قَدْ أَفْلَحَ الْمُؤْمِنُونَ
Successful indeed are the believers,
الَّذِينَ هُمْ فِي صَلَاتِهِمْ خَاشِعُونَ
Who are humble in their prayers,
Surah Al-Muminoon 23:1-2
Hence in order to obtain khsuhu' one must become a Mumin and Khushu' will automatically follow. Ive mentioned before Iman is not a matter of belief. Belief is a quality of a muslim not a mumin. A momin is one who truly has faith in God. How does one become a Mumin? Anyone can be a muslim, but not everyone can be a Mumin.