Imam As-Sadiq [as] said about the meaning of worship: “Worship is of three kinds: some people worship Allah, because they fear Him – so it is the worship of slaves; and a group worships Allah, Blessed and High is He, to seek reward – so it is the worship of hirelings; and a group worships Allah, Mighty and Great is He, because of (His) love – and this is the worship of the free, and it is the most excellent worship.” (al-Kafi)
Imam Ali [as] said: Verily, some people worshipped Allah being desirous (Of His reward) – so this is the worship of traders; and some people worshipped Allah fearing (His punishment) – so it is the worship of slaves, and a group worshipped Allah in gratitude (to Him) so this is the worship of the free. (Nahju ‘I-balaghah)
Imam as-Sadiq [as] said: ‘Verily people worship Allah in three ways: One group worships Him in desire of His reward, and it is the worship of covetous ones, and it is greed; and others Worship Him in dread of the Fire, and it is the worship of slaves, and it is fear; but I worship Him in His love – Mighty and Great is He and this is the worship of noble ones. (It is) because Allah has said: and they shall be secure from terror on that days (27: 89); and He has said, Say: ‘If You love Allah, then follow me, Allah will love you. . .’ (3:31). Therefore, whosoever is loved by Allah, he shall be among the secure ones; and it is a hidden position, cannot touch it save the purified ones.” (al-Ilal, al-Majalis and al-Khisal)
The above quoted traditions show that the highest form of worship is not done out of fear of hell, nor for the sake of Heaven, rather it is done out of sheer love and gratitude to Allah swt.
Our worship, which is the worship of slaves and business men, makes Allah swt a means to an end. He is not our final goal; He is only an intermediary to a final goal which is Heaven. We worship God because we want the material pleasures of Heaven, and this is different from wanting Allah swt.
On the otherhand the Ahlul Bayt and Awliya’ of Allah worshipped God out of love for Him, and recognising that He is worthy of their worship. To them Allah swt was the ultimate goal, and greatest prize. It wasn’t the rivers of honey or the mansions of paradise.
A few questions arise here:
(1) If the above is true, why did the Ahlul Bayt in many supplications seek Heaven, and ask to be saved from Hell?
(2) Why did they supplicate for Houris and palaces?
This is discussed below.
(1) Heaven and Hell
When we seek heaven we do so for its material rewards. This is the worship of the traders that is mentioned in the hadith. When the Awliya’ seek Heaven their minds are on something else. They want heaven because it is a place of nearness to Allah swt, not because of its material pleasures. Similarly, they fear hell because it is a place of distance from Allah swt. They cannot stand the thought of distance, and want only greater proximity.
Imam Ali [as] in Dua Kumail says:
Therefore (my Lord!) If Thou wilt subject me to the penalties (of hell) in company of Thy enemies and cast me with those who merited Thy punishments and tear me apart from Thy friends and those who will be near to Thee, then my God, my Lord and my Master, though I may patiently bear Thy punishments, how can I calmly accept being kept away from Thee?
I reckon that though I may patiently endure the scorching fire of Thy hell, yet how can I resign myself to the denial of Thy pity and clemency?
According to Imam Ali [as] the torment of the fire of Hell is severe and unbearable, but even worse than this torment is being kept away from Allah. In Munajat Sha’baniyah he says:
الهي ان اخذتني بجرمي اخذتك بعفوك, وان اخذتني بذنوبي اخذتك بمغفرتك, وان ادخلتني النار اعلمت اهلها اني احبك
My Lord, if You condemn me for my crimes, I will cling to Your forgiveness, and if You hold me for my sins, I will cling to Your granting pardon. If You haul me into the hell, I will tell its inmates that I love You.
When Asiyah [r] the wife of Fir’own was being tortured, she asked Allah swt to build her a house in Jannah. But the most important thing in her eyes was that this house should be ‘near you’.
وَضَرَبَ اللَّهُ مَثَلاً لِلَّذِينَ آمَنُوا اِمْرَأَةَ فِرْعَوْنَ إِذْ قَالَتْ رَبِّ ابْنِ لِي عِنْدَكَ بَيْتاً فِي الْجَنَّةِ وَنَجِّنِي مِنْ فِرْعَوْنَ وَعَمَلِهِ وَنَجِّنِي مِنْ الْقَوْمِ الظَّالِمِينَ
[66:11] And Allah sets forth, as an example to those who believe the wife of Pharaoh: Behold she said: “O my Lord! Build for me, in nearness to Thee, a mansion in the Garden, and save me from Pharaoh and his doings, and save me from those that do wrong”;
She didn’t say ”build for me a house in Jannah” or ”build for me a house in Jannah in nearness to you” rather she said ”Build for me, in nearness to Thee, a house in Jannah”
Being close to Allah swt was what she wanted.
(2) Supplicating for houris and palaces.
Imam Khumayni [r] in his book Adabu Salat addresses this issue whilst discussing the beliefs of those Muslims with a materialistic outlook:
But the love of the one who resides therein. 
Otherwise, what would, ‘Ali ibn Abi Talib (AS) do with houris and palaces? How could that great man be associated with the appetites of the self and the animal desires? The one whose worship is that of a free man, his reward cannot be that of traders.