Every time I get a new bag, I move my stuff right in, and I start carrying it right away. However, I find that in the first week of carrying it, my arm or shoulder feels a bit sore due to the difference in weight or weight distribution from the bag I was carrying previously. Does anyone else have that problem? It seems to happen to me every time, but I can never stop worrying that ultimately the bag will be too heavy or uncomfortable for me to carry long term during that first week.