If I travel at relativistic speed from planet A to planet B which are at rest relative to one another, I will be younger than people on A or B when I arrive. However how does this mesh with the fact that the change in proper time should be symmetrical, i.e. I should observe events on A as well as B as moving at a slower rate, so when I arrive at B why would I be younger? I understand this is similar to the twin paradox and other questions I have asked but I still don't understand how you can resolve the discrepancy since you remain in one inertial frame for the entire journey. Is it because I have to de-accelerate and thus change reference frames to arrive at B, and if so would the effect be the same if I never accelerated or de-accelerated from A to B I just merely flew past them?