In English, one might refer to "the life" to refer to a particular way of life: a profession, for example, or living in a particular place.
Does Dutch have such a meaning for "het leven" - such that this sentence could reasonably be translated "The life is hard, but I am harder"?
In Dutch, if there's suddenly a word with a definite article in front of it (de, het), lacking any other qualifiers or hints as to how it's meant, it usually means the most basic/important form of the concept. For 'the life is hard' to make sense, you'd need some kind of qualifier here: 'the wrestling life', 'the life of a smurf' or 'the life that I lead'.
If you want the sentence to make any kind of sense on its own, the previous sentence should refer to what kind of life is meant: 'I spend most of my time dressing up as a demonic easter to help parents punish their naughty children. The life is hard, but I am harder.'