Mental distress or agitation resulting from concern usually for something impending or anticipated - Webster 2. Money, family, job, school, social relationships, life, and death. Worry suggests a lack of trust in God. Worrying does not make anything any better. Some also fear the dying process as much if not more than death.
Death is the result of sin.
It is the ever present reminder that we all are sinners. Left to itself death's victory is to bring man to eternal damnation in hell. Jesus brought us victory over death and the devil. Paul knew that death for the believer was the time to be with Jesus forever. For that reason Paul desired death.