Very closely related to: How to behave with a colleague who suffered the loss of a close family member? and What is an appropriate response to the death of a coworker's loved one?
These questions ask about how to deal with a colleague after losing a loved one. In the past couple of months, however, two members of my family died from unrelated causes. I've mostly dealt with it now, but I've been examining how I felt and I'm not quite sure if I behaved appropriately.
My colleagues knew, and they've all offered condolences and support should I need it, as well as my manager offering me whatever leave of absence I need to go and deal with things. People close to me personally all noticed that there's something's not quite been right and I'm not really the same person I was beforehand. I've opened up to them when I've needed to, but I'm well aware that these things just take time, and this has obviously put a lot of strain on some of my personal relationships.
Fundamentally, though, I've just wanted to keep busy, get my head down, and carry on with work. I like where I work and I like the people I work with. I know that I've not been performing as well as I usually would. I've found myself more distracted and just generally a bit slow.
I wanted to keep taking on tasks, but I'm not sure how I could have tempered this with a sense of "It's going to take longer than it ought to". It might have been more worthwhile to just take the leave and let them get on without me, rather than attempting to make them carry on with only half of me. Maybe I could have made it clear that I just wanted to plod along and get stuff done for a bit.
If it's relevant, I'm a mid-level software engineer in the United Kingdom, but I imagine humans are quite similar everywhere.
How can I let my manager / colleagues know that my performance might suffer temporarily while grieving or dealing with a personal loss? Should I tell them?