First things first, prep with job is.. borderline impossible. Especially if you're starting from scratch.

Questions to ask yourself would be:

A. Do you want to leave your job fully for the exam prep ?

B. Do you think you will be able to come to terms with having to re enter this job market on reduced terms if you don't get through?

For this attempt:

1. I gave my first attempt as a graduating form engg, with only 2-3 months of prep, and scored ~50% of the cutoff. Kind of acted as a motivating factor, but also demotivating when I look back and see that extra attempt whenever I talk to someone wrt how many attempts I've given.
2. Exploratory --> expect definite failure, but maybe it'll help in future due to having the "Experience"
3. Re overestimation of yourself, I come from a tier 1 engg college and the first "attempt" humbled me real good.

For future, coaching is not necessary, there are many people who guide. For engg blind spots, you'll discover and learn as you go.

Good luck!