A slave should remain between fear and hope. For, the right and the approved kind of fear is that which acts as a barrier between the slave and the things forbidden by Allah. But, if fear is excessive, then the possibility is that the man will fall into despair and pessimism.
On the other hand the approved state of optimism is of a man who does good in the light of the Shari'ah and is hopeful of being rewarded for it. Or, conversely, if a man committed a sin, he repents sincerely, and is hopeful of being forgiven. Allah (subhaanahu wa ta'ala) said: {Verily, those who believed, and those who migrated and fought in the way of Allah, it is they who are hopeful of Allah's mercy. And Allah is very Forgiving, very Merciful.} (Al-Baqarah, 218)
In contrast, if a man indulges in sins and excesses, but is hopeful that he would be forgiven without doing anything good, then, this is self-deception, mere illusion and false hope.
Abu 'All Rowzbari has said,
"Fear and hope are like the two wings of a bird. If they are well balanced, the flight will be well balanced. But, If one is stunted, the Right would also be stunted. And, to be sure, if the two are lost, the bird will soon be in the throes of death."
Allah has praised the people of hope and fear in the following verse:
{Is one who worships devotedly during the night, prostrating himself or standing, fearing the Hereafter, and hoping for the mercy of his Lord (is equal to him who doesn't do these things)?} (Al Zumar, 9)
Hope then also demands fear. If that was not the case, one would be in a state of false security. Conversely, fear demands hope. Without that it would be despair.