Of all the cultivation methodologies, cultivating mana can lead to the most drastic changes in one's Definition. If one cultivates fire mana, he/she might end up an elemental, bound entirely to the ideal cultivated without any free will to think outside of the cultivated concept. To clarify, mana is defined in this discussion as Potentiality Defined by collective Will. The collective Will includes the Will that makes the World Laws, and thus mana can be expressed either in a softer and more nebulous system, or as a very narrowly defined set of rules. That is the biggest difference between mana and qi. Since mana is not under someone's aegis, it can be Defined by the world's Laws easily, while qi is only qi once under someone's Will, and is usually not able to be Defined by the world's Law.
Mana cultivation is very different than qi cultivation. Where qi cultivation gathers power to gradually shift the cultivator from the world Will's Definition to his/her own by making the outside energy part of his/her Definition, mana cultivation is about transforming the cultivator to match the mana. If there are thresholds for mana cultivation, they come when the cultivator's Definition is destroyed enough for him/her to gain control over that part of his/her existence. The cultivator has to rebuild that part of himself/herself, and if he/she fails to utilize his/her Will properly, the cultivator will deviate from the Path of Ascension, and will most likely become an Elemental bound to the Will of the world.
There are two additional ends for a mana Ascender. They can either merge with the Will of the World to become Aspects of it, or transform on their own to become an Aspect of a Concept with a much higher risk of dissolution. While merging does pose less risk and is useful for the Ascender who wishes to remain with his/her world for eternity, many Ascenders do not wish to be bound to another Will so intimately, and so try to Ascend on their own. Almost all fail, but enough survive that it is actually treated as an option.