I remember there was one saying at work: Thursday Is the New Friday and Friday Is Actually the Weekend. So no one wanted to work. 😀
I am a person who loves working (especially on my own projects) so do not differentiate these days.
Anyway, how do you make yourself not fall into that "day-off" mood?
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For me, it is usually:
⏰ Wake-up early
📝 To have a list of activities I need to get done
☝️ Contingent reward (when I am done with this I can allow myself this) – it is a kind of mini-motivation to me.