The Drawbacks of Magic:
Unlocking this highly active and continuous brain state heightens the mage’s nervous system. In their altered state of mind the mage becomes super sensitive to everything around them.
Consequently while their senses speed, and reaction time dramatically increases, their pain tolerance dramatically lowers. A mage stubbing his toe may feel as if someone had taken a hammer to it. The heightened sensitivity is a double edged sword.
Extensive dosing of ingested reagents can leave a mage with a struggling immune system, leaving them susceptible to serious illnesses. Psychological effects, can include minor depression, mood swings, and increased paranoia. Losing one’s focus while under the influence of sacred mushrooms or herbs can cause a mage to be lost temporarily in a hallucinogenic haze.
An advanced spell may kill a mage if the mage’s body is not strong enough to adequately handle the amount of physical stress that certain spells can impose on the body. An injured (or ill) mage should be wary of expanding large amounts of energy less their body succumb to the injuries.
Additionally it is generally recommended that a mage who is injured at least numb their pain before altering their state of mind, less their heightened senses amplify their pain which usually results in making concentrating and thus spell casting very difficult. A mage must be able to maintain a certain degree of focus to complete or maintain a spell, an interruption of a mage’s concentration will almost always cancel any spell under a mage’s management.
For most beings advanced magic requires crystals. These can be stolen or destroyed or lost. Many magic users are fairly limited without gemstones (or items bejeweled with crystals), they can make very small changes happen around them but they don’t have anything close to precise control over magic. Mages get fatigued after extensive use and have been known to fall into a temporary comatose due to spiritual exhaustion if spell casting past their bodily limits.
Spell effects are generally temporary. Attempting to create a spell with a permanent effect such as in item enhancement will cost a tremendous amount of energy that can take a mage’s life.
Nothing appears from thin air, you can manipulate things that already exist (set them on fire, move them, explode them), but you can’t conjure anything that isn’t here (make wall of brick appear). Remember, though, that turning water into ice is not turning one thing into another and collected mana can be turned into other things, but then you run into the problem of…
Places have a finite amount of magic available. When one uses magic, they draw mana out of the environment to power it but there is only so much mana in a given area, some more than others. If one were to use up all of this mana, they would have to wait a while for it to replenish. The same would apply for magic techniques that uses one’s inner magoi or mana capacity, which can also be depleted until the being is able to draw more into iteself.