What was the most difficult part of the journey “from the Varangians to the Greeks” and why?

The most difficult part of the way in this direction was the crossing from the Lovat River to the Dnieper. This was due to the fact that the ships had to be dragged.
It is known that “the way from the Varangians to the Greeks” was the largest trade route passing through Kievan Rus from Scandinavia to the Byzantine Empire. This path contributed to the rapid development of cities, especially Kiev, which in the Middle Ages was the center of trade in Eastern Europe.