Allahumma ah’yini maa kaanathil hayathu khairanli wathavaffani idhzaa kanathil wafaathu khairanli.

اَللّهُمَّ أَحْيِنِيْ مَا كَانَتِ الْحَيَاةُ خَيْرًا لِيْ وَتَوَفَّنِيْ إِذَا كَانَتِ الْوَفَاةُ خَيْرًا لِيْ

Meaning:
O Allah! Keep me alive as long as life is better for me, and let me die if death is better for me.
(Book: Bukhari 5671, 6351)