You have no maximum hand size.
At the beginning of your upkeep, you gain 1 life for each card in your hand.
If multiple effects modify your hand size, apply them in timestamp order. For example, if you put Null Profusion (an enchantment that says your maximum hand size is two) onto the battlefield and then put Venser’s Journal onto the battlefield, you’ll have no maximum hand size. However, if those permanents enter the battlefield in the opposite order, your maximum hand size would be two.