We have no clear idea what's next. I mean, after this life. Really.
We speak of heaven, and "the next adventure" but we have for this inevitable end that each of us will meet the most extreme dearth of detail regarding any important thing imaginable. That's why life after death books sell so well, and it's why psychics and clairvoyants stay in business.
One thing seems likely to me, having studied this for decades. It will matter then what we do now. We should treat each other in this life as well as we possibly can. For theists, it's an obligation. For atheists and agnostics, it's a bold dramatic gesture. For all, it's an exercise of radical freedom, achieved with difficulty - not to react slavishly and reciprocally to what others do to us, but to set new standards for what those others need to have done for them. Each of us is called to be a pioneer of elevating action. Each of us is called to heroic grace.
We should treat others exceedingly well, despite what they sometimes do to us, not just because of what they are created to be, but because of what we ourselves are created to be. The fact is that we deserve the effects of such actions as those we ought to perform. Many great thinkers, such as Plato and Shakespeare's Hamlet, have understood this. We all need to, as well.
The relationship between the now and the hereafter is simple. The now is limited. We know that. And it will affect whatever hereafter there is - even from an atheistic perspective, for what is now created and done will never cease to have been, forever into the future. Every act is eternal. The full story of reality is vastly and everlastingly different, depending on what we do now, day-to-day. There's always the possibility of demeaning behavior or elevating action - it's left to be our choice. What then will we do?