I'm a lazy person, just copying the information from the source I used and juxtoposing it with the other information while cutting out the irrelevant parts and editing it to make sure you know what's entirely important.
https://www.sociotype.com/socionics/...on_elements/Si
Si is associated with the ability to internalize sensations and to experience them in full detail. Si focuses on tangible, direct (external) connections (introverted) between processes (dynamic) happening in one time, i.e. the physical, sensual experience of interactions between objects. This leads to an awareness of internal tangible physical states and how various physical fluctuations or substances are directly transferred between objects, such as motion, temperature, or dirtiness. The awareness of these tangible physical processes consequently leads to an awareness of health, or an optimum balance with one's environment. The individual physical reaction to concrete surroundings is main way we perceive and define aesthetics, comfort, convenience, and pleasure.
Introverted intuition is an introverted, irrational, and dynamic information element. It is also called Ni, T, temporal intuition, or white intuition. Ni is generally associated with the ability to recognize the unfolding of processes over time (how one event leads to another), have visions of the past and future, develop mental imagery, and see intangible hints of relationships between processes or objects. Types that value Ni always like to have in mind a specific plan for how their life will develop in the future. Thus they have little time for the concept of "living for the moment" or "making the best of the present". <<< Depends, I do live for the moment, as this is entirely the best answer.
They generally engage in pure leisure activities only for short periods of time <<< Entirely false, I have 1000 hours in the Operational Art of War IV, and watch content on video games religiously. Shout outs to Simple Flips, a savant worse than me. Currently, I'm watching UFC in the background.
and even then their leisure activities generally involve a psychologically demanding or competitive aspect. <<< Nevermind. I can read. Insert Sterlitz joke here.