Ibn Al-Qayyim Al-Jawzi (in Madarij As-Salikeen) said:
The heart in its journey towards Allah (سبحانه وتعالى) is like a bird; its head is love, and its two wings are hope and fear. When the head and the two wings are sound and healthy, then the bird will fly well. If the head of the bird is cut off, it immediately dies, and when either or both wings are deficient, the bird cannot fly properly and it may become the victim of a hunter that passes by.
From this analogy we learn that without love of Allah we cannot successfully “journey towards Him,” and without hope in Allah’s mercy or fear from His punishment, we may be easy victims for Shaytaan (أعوذ بالله من الشيطان الرجيم).
So the Muslim, then, with resolute love for Allah  (سبحانه وتعالى), lives between hope and fear. He “call[s] upon Allah out of fear and hope,”  and he “forsake[s] [his] bed, to invoke [his] Lord in fear and hope, and [he] spend[s] (charity in Allah’s Cause) out of what We have bestowed on them.” 
Imam Ahmad recorded from ‘A’ishah (رضي الله عنها): I said: “O Messenger of Allah, ‘And those who give that which they give with their hearts full of fear, because they are sure to return to their Lord,’  are these the ones who steal and commit zina and drink alcohol while fearing Allah?” Ibn Abi Hatim recorded that the Prophet (صلي الله عليه وسلم) said: “No, O daughter of As-Siddiq, they are the ones who pray and fast and give in charity, while fearing that it will not be accepted from them,” (i.e. it is these who hasten in the good deeds.) At-Tirmidhi recorded something similar.
‘Umar ibn Al-Khattab (رضي الله عنه) said: If an angel had come down and announced that everyone would enter paradise except one person, I would fear that I would be that person. This is ‘Umar ibn Al-Khattab, the second khalifa, and one of the ten promised paradise! Subhanallah!
And how do we increase our fear of Allah’s punishment?
Ibn Mas’ood (رضي الله عنه) said: “If a person has knowledge, he will fear Allah.” So we should increase our knowledge. And The Prophet (صلي الله عليه وسلم) said, as narrated by Anas (رضي الله عنه): “I swear by The One in Whose Hand my soul is, if you saw what I saw you would laugh little, and cry excessively.” The people said, “O Prophet of Allah! What did you see?” He (صلي الله عليه وسلم) replied, “I saw Paradise and Hell.” [Saheeh Muslim]. So we should reflect on the punishment of “him who ‘tagha’ (transgressed all bounds, in disbelief, oppression and evil deeds of disobedience to Allah), and preferred the life of this world. Verily, his abode will be Hellfire,” , the “Fire whose fuel is men and stones.” 
Anas reported that the Prophet (صلي الله عليه وسلم) entered upon a young boy who was dying. The Prophet (صلي الله عليه وسلم) asked: “How are you?” The boy replied: “O Messenger of Allah, I am in-between hoping in Allah and fearing for my sins.” The Prophet (صلي الله عليه وسلم) said: “The like of these two qualities do not unite in the heart of a servant except that Allah gives him what he hopes for and protects him from what he feared.” [a hasan hadith – Collected by at-Tirmidhee and Ibn Maajah, and authenticated by Al-Albaanee in Ahkaamul-Janaa’iz (no. 2).]
‘Umar ibn Al-Khattab (رضي الله عنه) also said: and if the angel had come down and announced that everyone will enter Hellfire except for one person, I would hope to be that person.
And Allah (سبحانه وتعالى) says:
وَلاَ تَيْأَسُواْ مِن رَّوْحِ اللّهِ إِنَّهُ لاَ يَيْأَسُ مِن رَّوْحِ اللّهِ إِلاَّ الْقَوْمُ الْكَافِرُونَ
Translation: and never give up hope of Allah’s Mercy. Certainly, no one despairs of Allah’s Mercy, except the people who disbelieve.” [Surah Yusuf, verse 87]
And so “to your Lord (Alone) turn (all your intentions and hopes and) your invocations.”  And ask yourself:
مَّا لَكُمْ لَا تَرْجُونَ لِلَّهِ وَقَارًا
Translation: What is the matter with you, [that you don’t fear Allah (His punishment), and] you don’t hope for reward (from Allah, or you believe not in His Oneness)? 
[قُل لاَّ يَسْتَوِي الْخَبِيثُ وَالطَّيِّبُ وَلَوْ أَعْجَبَكَ كَثْرَةُ الْخَبِيثِ فَاتَّقُواْ اللّهَ يَا أُوْلِي الأَلْبَابِ لَعَلَّكُمْ تُفْلِحُون [1
Translation: Say (O Muhammad): “Not equal are the filthy things with the wholesome, even though the abundance of evil filth may please you.” So fear Allah much [(abstain from all kinds of sins and evil deeds which He has forbidden) and love Allah much (perform all kinds of good deeds which He has ordained)], O men of understanding in order that you may be successful. [Suratul Ma’idah, verse 100]
 وَادْعُوهُ خَوْفًا وَطَمَعًا [Suratul-A’raaf, verse 56]
 تَتَجَافَى جُنُوبُهُمْ عَنِ الْمَضَاجِعِ يَدْعُونَ رَبَّهُمْ خَوْفًا وَطَمَعًا وَمِمَّا رَزَقْنَاهُمْ يُنفِقُونَ [Suratus-Sajdah, verse 16]
 وَالَّذِينَ يُؤْتُونَ مَا آتَوا وَّقُلُوبُهُمْ وَجِلَةٌ أَنَّهُمْ إِلَى رَبِّهِمْ رَاجِعُونَ [Suratul-Mu’minuun, verse 60]
 فَأَمَّا مَن طَغَى وَآثَرَ الْحَيَاةَ الدُّنْيَا فَإِنَّ الْجَحِيمَ هِيَ الْمَأْوَى [Suratun-Nazi’at, verses 37-39]
 فَاتَّقُواْ النَّارَ الَّتِي وَقُودُهَا النَّاسُ وَالْحِجَارَةُ [Suratul-Baqarah, verse 24]
 وَإِلَى رَبِّكَ فَارْغَبْ [Surat-Ash-Sharh, verse 8]
 مَّا لَكُمْ لَا تَرْجُونَ لِلَّهِ وَقَارًا [Surat-Nuh, verse 13]
Abdul-Bary Yahya. Lecture. AlMaghrib. Purification of the Heart: Love, Fear & Tears. Part 2: The Two Wings of the Believer.
Abu Iyaad As-Salafi. Salafipublications.com. On Eeman, Ibaadah and Tawheed: Their Link and Interrelation. Lesson 3: Love, Hope and Fear.
Tafsir Ibn Kathir