Hello, Iluuvpups! I don't know what to say, either. To have friendships fade -- no matter the reason -- is painful. Seems it's all intertwined: the tumor, the depression, the social strains. If it weren't so upsetting, it would almost be "interesting" to see which relationships survive the turmoil.
Wishing you comfort, old friends who won't wither, and new friends
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My dog

mastered the "fetch" command. He would communicate he wanted something, and I would fetch it.