1) Forgot to carry a tiffin box - Everyone needs a tiffin to eat in when you go trekking. They do not provide you with plates and spoons and forks. I had certainly expected them to give it to me. However, the trek wasn't my Mumbai elitist travel and I had to learn better for next time.
2) Carried a towel with me - As humorous as this sounds, it is impossible to bathe on a mountain when it is freezing outside in super cold water. Since I am from Mumbai and I haven't explored much of the mountains before, I carried a towel with me expecting to get hot water to bathe on the mountain. However, there was no hot water and I failed to bathe for a week. It did make me feel gross but coming back and bathing was heavenly. The towel only occupied extra space in my already heavy bag.
3) left the tent open at night - I left the tent open at night. I shut the main zip but I forgot to shut the zip which covers the tent net. As a result, the tent got really cold at night and I almost froze. My tent mates were extremely pissed at me in the morning because it was my fault. However, they realised it was my first trek and let it go. In fact, they were very supportive and asked me if I needed help with anything.
4) forgot to pee - I forgot to pee at night before I slept and I woke up at 1AM to pee. It was cold outside, I couldn't walk till the bathroom stalls. I literally peed outside near the tent and I was scared that people would hear me pee. I am so glad that no one heard it. However, my sleep for the night was ruined and I was exhausted when I was trekking the next day.
5) did not carry enough water for the way - Out of whatever trekkers teach you, the most important thing they always say is carry enough water because not having water on the mountain puts you at the risk of dehydration and you may even get hit by AMS which will ruin your trek. ALWAYS carry enough water so that you don't have to rely on others. My water ran out on the way and I couldn't even walk more. My trek guide had to borrow water from other people to help me to go ahead. It was really sad!
The key is that everyone makes mistakes when they trek the first time and they learn from those. However, you can also learn from my mistakes to be a better trekker.