Players should be allowed one mistake; this would significantly increase the number of decent games. As it is, any mistake can ruin several hours of gameplay. For example, one player's guards might be slightly better positioned, or a single unit's morale might allow it to stun neutral creatures for the entire battle. This can be decisive at the beginning against a truly strong player, while a weaker player hopes their opponent will make a mistake or simply give up.
P.S. Thanks to those who play without using save-scumming (loading saves). I won't say anything more, as these are games of skill.

Denis, I'm sorry, but you're a top-10 player, and save-scumming shouldn't bother you. We're all in the same boat; most of us have families and children. Complaining about this and blaming it on some random event in the game is inappropriate, especially coming from a player of your caliber.
I wasn't expecting any misclicks from you. We both followed the tournament rules. A strong player is strong in all aspects, including assessing the risks in the game. So, you should blame yourself. Adding the option to save-scum to the rules on the League, as well as on other Heroes of Might and Magic websites, would be complete nonsense.