Is it obligatory to fulfill a vow to fast two consecutive months and donate a sum of money, which was vowed out of fear of death during a mild illness?

It is disliked to make a conditional vow, but fulfilling it becomes obligatory if the condition it was based on occurs. If you are unable to fulfill it, you must pay the expiation for breaking an oath (kaffarat yamin (definition)). Fear of death is natural and is praiseworthy if it motivates obedience and asceticism in this world. However, fear that hinders action and fills one with sadness is blameworthy in Islamic law, and its possessor should remove it by knowing that what is with Allah is better for the righteous, and that death in obedience to Allah is a comfort.