I think that some people may very well have different things in mind with "my dream" versus "my dream in life." Most significantly, "my dream" can include wishes unconnected to reality, such as
My dream is to ride a white dragon like the one in that Anne McCaffrey book.
as well as more down-to-earth ones such as
My dream is to buy an inexpensive 1992 Toyota Tercel with all four hubcaps still in place.
and ones that fall somewhere in between such as
My dream is to become a key member of Justin Bieber's entourage.
In contrast, "my dream in life" seems most appropriately tied to a long-term aspiration involving career or love or artistic fulfillment. Of the three "dreams" listed above, only the one involving membership in Justin Bieber entourage—which, remarkably, combines aspirations for career, love, and art—would qualify as a "dream in life," strictly understood.
Of course, many people may not feel constrained to use "dream in life" only in connection with attaining some life goal, as opposed to describing some magical or mundane dream of the moment; but the distinction is available to them if they choose to make use of it.