Swords crashing, lives being forfeit and the general sense of urgency surrounds you in an ever so fascinating game of Castle Crashers. This game is designed to be a multiplayer experience, and anything less will make the game very much a trivial challenge. This is sort of the way things go however in games designed to be multi player. the game makers will intentionally leave the game just as challenging as if you had four player, even if you just have the one. Games like Castle Crashers, Scott Pilgrim and even games like splinter cell, basically punish those players who decide to game alone.
Go out and meet some friends. The inclusion of online multi-player is nice, but it can not substitute for having friends right by your side. Not only will you have 0% chance of the game being dropped and your hours of racking up xp / kills being virtually erased, (well except for when an upset friend drop kicks your tv because you stole the last health fruit), but you can more easily collaborate on strategy without having to buy extra crap that still has your online partner sounding like a robot getting eaten by a walrus.