It might be the case that

you feel more secure only when you're busy working or taking care of things. It may have stemed from your childhood when your parents' approval came only when you were doing your chores. It conditioned a reflex in you that connects feeling secure (安全感）and being busy. Or putting it the other way: you feel insecure if you don't feel busy.

When you feel lethargic at work, it might be your unconscious self telling you: hey, I've been used long enough; I need some pampering too.