I am currently employed by a small market research firm (7 employees) and the firm is a really close-knit community. I like my co-workers, including my boss. Especially my boss is a very nice person - giving good advice and when my father died last year he was very tolerant about unscheduled days off etc.
Unfortunately, I feel the need to move on because I cannot improve myself at this job - there are too few customers to warrant new / different projects. Also, my girlfriend is stuck at a really bad workplace - but the chance that she gets a job in this region is bad.
But I am feeling intensely disloyal when considering quitting and I am really uncertain how to tell it to my boss.
Also, I am doing a very special job which cannot be done by anyone else in the company - so my boss needs to find a replacement fast. To clarify this: I am a statistician and the only one in my firm. Worse, my work is a very important step and all people are need me to finish my work, before they can start. Other people know bits and pieces of my work - but they don't have the kind of training I have. Even when I am ill or on vacation I am remoting in and doing some work, because I don't want the whole firm to wait for me.
I am living in Germany, so I have 3 months’ notice period.