It didn't happen out of the blue tho - to make a long story short, that firm wasn't the right place for me; not my kind of job.
Yeah, it was chemistry, but not all chemistry is the same. What we did most was production of reference materials, and in that line of work pedantry becomes almost a lifestyle. That's a main problem: I am almost allergic to pedantry; I find it to be utterly uninspiring (unless it's pedantry I have chosen for myself).
Then, at least from my point of view, I was often given unclear or even conflicting instructions (like "we must strive to keep the temperature at 20 °C", soon followed by "anything between 18 and 23 is fine"). That put me in a difficult position.
The final result was that often the work held little interest for me, and I ended up winging it until 6pm. Needless to say, my performance on the job wasn't stellar, and the bosses noticed it. But they have long-term projects and want someone who will devote all of himself to the job - so, I was asked to kindly leave the firm.
I accepted rather readily because there wasn't much for me in there anyway - yes, maybe there was the prospect of future advancements or improvements, but it wasn't enough.
So here I am. As they say, the important thing is not to never fall, but to find the strength to stand up again. I'm quite willing to even completely change line of work if that means finding the right one for me.