I recalled Shaykh Muhammad bin Yahya an-Ninowy speaking furiously about the need to clarify the commonly accepted definitions on being dead and being alive. He was absolutely right. Prophet Muhammad s.a.w was in fact the first to define those terms - things that we take for granted except when we are terminally ill.
The Prophet s.a.w said:
"He who remembers his Lord
and he who does not remember his Lord
are like the living and the dead." - Al-Bukhari.
O son, know that remembering Allah is the one and only determining factor.
"And remember your Lord by your tongue and within yourself, humbly and in awe, without loudness, by words in the morning and in the afternoon, and be not among those who are neglectful." (Qur'an: Al-Araf 7:205)
I also recalled a beautiful du'a made by Shaykh Abdul Qadir al-Jilani:
'O Allah, let Your remembrance
be our nourishment
and let Your nearness
be our wealth.'
O son, remembering Him is indeed nourishing; it makes us alive!
Ya Hayy, Ya Hayy, Ya Hayy!
Further reading: The Virtue of Remembering Allah