Should I be honest and write about why I know it is time to part ways in the resignation letter. If I do that, how long should the resignation letter be, for it not to be too long?
Should I write about things I dislike in the company culture? Or should I just be formal, clear and polite:
Taken from another question on WP.SE:
I regret to inform you that I will be resigning my position with [company], effective on [date]. Please consider this note my official [number] weeks' advance notice. Let me know if there are special duties, such as helping to train my replacement, that you want me to spend the remaining time on.
Adding the next bit could make it more personal:
I have family issues that take time/I want to focus on my thesis/health issues and I can't work at full efficiency anymore. I am thankful for the time I worked at company X... I wish you all the best
Mentioning what I dislike about the company doesn't feel like a good idea, intuitively.
I am inclined towards a formal resignation letter with no reasons mentioned at all. I found a resignation template on intranet site, it is close to the first fragment I posted.