A: It may not be possible to make eternal decisions in this earth life, although we can certainly make decisions that contribute to our eternal life. Like the process you describe in your question, we can choose to cooperate with our Thought Adjuster, we can decide that God's will is what we want in our lives, and we can reinforce those basic decisions with the every-day kinds of choices that we all face. By doing this, we grow our soul—the immortal part of us that will survive the death experience. And that is the eternal part of us that will eventually fuse with the TA. Even if we haven't made the "final decision" here—still, by contributing to our soul's growth, we are just that much better able to eventually make that decision when we are really ready.
Here's an abbreviated quote that might be helpful:
(40:8.1) ...practically all surviving mortals are fused with their Adjusters on one of the mansion worlds or immediately upon their arrival on the higher morontia spheres...
For me, it is enough of a hope that my faith is sufficient to ensure that I will survive to wake up on the Mansion Worlds, and I think that is the best that most us can wish for at this juncture in our lives. And that's pretty good news! The Urantia Book teaches that fusion with the TA may be a long way off, even after we survive. That kind of decision is not made lightly, even though we may feel that we want it while we are here. As far as I know, only Enoch was able to achieve it here on Urantia, when he went up in a "flash of fire." The Urantia Book says that he was "the first," so maybe there have been others since then, but I don't know...Through our continuing purification, spirit identification, and education on the Mansion Worlds, we can hope to become far better equipped to make that kind of eternal decision when the time is right.
(47:8.3) This is a brilliant age for ascending mortals and usually witnesses the perfect fusion of the human mind and the divine Adjuster. In potential, this fusion may have occurred previously, but the actual working identity many times is not achieved until the time of the sojourn on the fifth mansion world or even the sixth.
Just for interest, you might like to read about Death and Translation on the Spheres of Light and Life. I think we here on Urantia are going to be waiting a long time before that becomes a reality, but someday...
Thanks for this interesting question!"