I finished the game under 20 hours in my first playthrough and it was amazing so I was excited to 100% the game so I could experience everything the game had to offer. But, the day I finished it I had to go somewhere for a week and that meant no more God Of War. During the middle of the week, I told my cousin to try it out and he began playing but I forgot to save my game manually. So, when my cousin started a new game, all the autosaves got overwritten which meant that I lost everything that I previously had done. I came back from my short vacation and when I saw that my saved game had been lost I had to play everything again because only then can I unlock the other realms to explore later on.
I grinded for about 15 hours and then I finished the Main Story again and I actually enjoyed it more because this time I exploited the game's mechanics. I upgraded all of my gear and looked for hidden treasures which made it easier for me to beat the bosses. By the time I was done with my second playthrough, I realized that I was much better off than my first playthrough. And now I have a bunch of stuff that I didn't have in my first playthrough. I guess this pretty much says that when you play a videogame, you should always enjoy it to its maximum because it really changes the overall experience.