[Yes it's different from transmigration, Reincarnation is rebirth of a soul in a new body, a new body not a already existing body like transmigration.
Now why is reincarnation so terrible? First of your a helpless baby that can't do anything other then eat, sleep and sh^¥ for years until your old enough to communicate and go to school hopefully and then more years of constant agony of acting like a kid until your older...
Sorry I got side tracked reincarantion is torture for the weak willed but it's good practice for patience and patience... It's pretty awful, any since you have a new body train in flexibility, control your breathing and endurance which will help in the long run no matter what.
Now the main problem with reincarnation is adaptability you need to adapt to your new life or else your be a outcast without commen sense. You see most people don't bother to learn about science, biology and stuff like that thinking it's identical to your old life well it isn't and now your wondering why physics isn't the same in a plan if existence that has difference laws like a idiot.
So the main thing to know about reincarantion is it sucks and you need to be adaptive and patience.