@Tomaloc
Yes I did cashed out twice. At first, I never thought of moving up since I am only playing this part-time since I have a job. (more of just a hobby thing).
However, I figured 2NL is just too loose and there is no way I could improve as a poker player (though I'm sure I will continue cashing out). I have been trying to improve my redline but no luck, its like a -10 degree slope, because fold equity in this limit is close to non-existent.
I'm not trying to minimize the train-wreck feeling you get after a session like that, but if that is your worst session ever, you have a lot to be thankful for.
Actually, I did had a more devastating downswing (which I will post later), but it is much more of an experiment in 5NL and I am not playing my comfortable style so I guess the result is expected, so I was able to accept that. However, when I moved down to 2NL today and played my solid approach on today's 2NL session but lose that much. Maybe that's why I'm upset.
The effect of a session like this is to provide perspective. The next bad session won't seem so bad, if is not as bad as this one. Sometime -- hopefully far -- in the future you will have a worse session, which will become the yardstick to measure bad sessions agains.
-Thanks, this helps.
Yes, you are right, but as Tomaloc says, the yellow line only applies to hands where you are ALL-IN. In all other cases, it just tracks parallel to the showdown or non-showdown lines.
-Thank you both of you, I'll do some hand filtering later.
My advice: Move up
Play a session at the next highest limit to see how it feels.
-Actually, I did. I played since Aug 21 until yesterday and this is what happened:

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First, I 6-tabled and played a solid TAG but soon realized that I could not crush 5NL with my TAG-nittish style, SOOOO..... I experimented using the stats below:

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1. I am not too alien of using the stats above (though it shows negative profit for now). If you refer to my overall 2NL graph, you'll notice that my winnings improved greatly on the last third-half. This is because I transitioned to a semi-LAG (if there is such a thing). The LAG style worked on my first the days on 5NL, however, it backfired eventually and I am currently doing my homework to fix it. MONEY BURNED but its ok I'll get it back soon. 
2. My main goal or mission on moving to 5NL is to have a graph with an acceptable redline. I am convinced that most profitable 2NL players may have a downward redline because as I've said, fold equity is not that reliable on this level. I would understand if you guys think that I am a fish for risking my BR for this stupid goal, since anyone could still be a winning player even with a downward RL. However, what can I do? I want to improve it. 
My unattractive 2NL redline:

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============MY THOUGHTS ON 2NL vs. 5NL:===================
1. I think 2NL-5NL may be one of the hardest limit transition. I am not saying that the high stakes transitions are easy. However, based on my observation, advanced skills needed to crush high stakes poker are mandatory starting in 5NL. On 2NL, anybody could crush it half-asleep provided that you play ABC poker, while a lot of 5NL regs are 2NL graduates like me who are in study mode and are absorbing and applying poker concepts little by little. I believe that by the time I crush 5NL, I would have learned the most important skill of all... THINKING!
2. I decided to move back down 2NL while studying more. I am currently trying to learn about post-flop concepts and at the same time having enough BR for 5NL.
Anyway, thank you for your insights guys... Good luck at the tables ♠_love: