This verse is very similar to 10.39, and translators are referred to that discussion.

Would save his life is translated “wants to save his life” by Moffatt, Phillips, and New Jerusalem Bible. New English Bible translates “cares for his own safety,” and Barclay “keep his life safe.” An American Translation renders “preserve his own life.” The word which appears as life in so many translations actually has “soul” as its first meaning. But all scholars agree that here it is used of the total person, without an assumed distinction between “life” and “soul.” Traduction œcuménique de la Bible, which translates “life,” has a footnote stating that both Hebrew and biblical Greek frequently use this noun as an equivalent of the pronouns “I,” “you,” and “he” or “she.” Moreover, in the Lukan parallel (9.25) to this verse, the pronoun “himself” is used in place of life.

Some translations of would save his life have the idea “wants to keep on living (forever).” This is probably not the best rendering. “Wants to keep his life safe” or “considers his life of greatest importance” are better.

Similarly, it is probably better not to render loses his life to mean “if someone dies” or, worse, “commits suicide,” although it can be understood as a reference to martyrdom. Expressions of self-denial such as “is prepared to lose his life” (Barclay) or “considers his own life as unimportant in order to become my disciple” are better.

Will lose it and will find it are normally expressed as “will not (or, will) have true life” or “will not (or, will) have (the) life that doesn’t end.”

For my sake may be clear in the context, but if not, “to become my follower” or “because he is my disciple” are possible.

The combination of the verbs would save … will lose … loses … will find raises some questions regarding the time perspective of this saying; that is, should it be taken in relation to the disciple’s life in the world here and now, or does it point toward life after death? In all probability the saying includes both perspectives; a footnote in New Jerusalem Bible describes the saying as a “paradox” because it oscillates “between two senses of human ‘life’: its present stage and its future….” The verse may then be translated “Whoever considers his own life to be of supreme importance will never experience true life. But whoever denies the importance of his own life in order to become my follower will experience true life.” In place of “true life” it is possible to use “eternal life.”

Quoted with permission from Newman, Barclay M. and Stine, Philip C. A Handbook on the Gospel of Matthew. (UBS Handbook Series). New York: UBS, 1988. For this and other handbooks for translators see here .