Debian upgrade causes many complications - best upgrading practices?

Question

I upgraded my Debian Jessie KDE system last night by running apt-get update, apt-get upgrade, apt-get dist-upgrade, and apt-get autoremove. Immediately after it began to malfunction so I checked /var/log/apt/history.log and as it turned out, these sequence of commands removed Skype, libraries that NetworkManager uses, libraries that KWallet uses, among others I'm sure. Attempting to re-install these software brings about more problems, so I'm thinking about doing a fresh install. My questions are, how common are detrimental upgrades such as this one and how to prevent them in the future? Also, what did I do wrong here? Usually every time I login, I run these sequence of commands to make sure all software is up to date.

sources.list:

deb http://ftp.us.debian.org/debian testing main contrib non-free
deb http://ftp.debian.org/debian/ jessie-updates main contrib non-free
deb http://security.debian.org/ jessie/updates main contrib non-free

deb-src http://ftp.us.debian.org/debian testing main contrib non-free
deb-src http://ftp.debian.org/debian/ jessie-updates main contrib non-free
deb-src http://security.debian.org/ jessie/updates main contrib non-free

sources.list.d contains 'bitmask.list' with the following content:

deb http://deb.bitmask.net/debian jessie main

/var/log/apt/history.log output of the upgrades that caused the problems: http://pastebin.com/raw.php?i=83ck0HiU

Answer 1

Your sources.list shows that you're pulling from the testing repository, not just Jessie. So you aren't running straight Jessie anymore, but a mix of Jessie and Stretch. (Maybe this is a result of your skype installation?)

Also, you should very rarely need to apt-get dist-upgrade. The best practice for updates is to use the apper GUI to regularly check for updates and upgrade your packages. Once you're on a stable Debian release you should mostly only get occasional security updates.