The same with the mind. what the mind thinks? what thoughts arise int he mind? One may assume that these can be controlled. Thoughts result from sensory inputs and accumulated thoughts. I can neither prevent or force myself to a thought. Events presents itself. it is perceived by the senses, Thoughts occur in the mind. It is clear that I cannot control the events. they are due to my past. similarly I cannot control the thoughts. neither can I control my actions. Similar to taking care of the body I can attempt to take care of the mind, force only good thoughts, avoid bad thoughts, and so on. and it will result in an apparent mental fitness.
If a particular event occurs, the event creates a set of thoughts. some so intense it breaks me down. I cry. weep like a baby. (of course it appears based on the 'strength' of the mind), There is neither a need nor a possibility to change any of this. If the thoughts of some of the finest moments in my past haunt me and paralyzes my thoughts of present day, let it be so. just like the body is in constant action, mind is in constant action, it creates countless thoughts about current experiences, memories and also fantasizes and worries about the yet to unfold future. That is the job of the mind. so I should let it happily do its job.
Just like a physical fitness creates an apparent improvement in the "general" lifestyle , so will a mental fitness create an apparent improvement in the "general" lifestyle. But...No amount of physical fitness can save the body if a truck falls on it, similarly no amount of mental conditioning will save its breakdown on certain events.