We could see it as one long lifetime, with different chapters, that make up the different lives in different bodies. So we still need to live as if there is only the now. And we need to be aware of the repercussions of our actions beyond this body, which, as you say, implies the need to to be conscientious.

The literatures on life and death talk about reincarnation but we have little if any personal experience, is it is hard to believe in reincarnation. Curiously, if there is no reincarnation, then no worries - we die and that's it. If there is reincarnation, then we carry on based on where we left off, so better we act accordingly. The choice is up to the individual. It may be better to prepare and live as if there is reincarnation.