I do this often also. Every time I start a new manga, I don't read anything else for a few days and it's difficult to pick up where I left off what I was previously reading. It's the main reason why I get behind on manga. The second reason is that they aren't completely scanlated so I have to put them on hold. There are many series that I've forgotten about because I didn't have a manga list until recently.
Character deaths have occasionally driven me away, but I usually continue reading after a 'mourning period' : after
Spoiler (mouse over to view)
Hide's death
in Tokyo Ghoul I cried floods of tears but when I finally got myself to read Tokyo Ghoul: re I was rewarded in the end.
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...Hop!