Spending a weekend alone on purpose is different from being left out. Notice which one you chose.

The same empty Saturday feels completely different depending on how it came about. Chosen, it is a rest. Arrived at because nobody asked, it is something else, and worth being honest about rather than relabelled as looking after yourself. Both are survivable and they need different responses, which is what makes the distinction useful rather than harsh.

Ask yourself which one this is. If you chose it, enjoy it and justify it to nobody. If you did not, you can do something about it this week, which usually means being the one who sends the message rather than waiting to be included.