I'd like to refer you to the image/phrase that I see floating around my Facebook feed every so often.
"A one hour workout is only 4% of your day. No excuses."
Only YOU can determine what is an "excuse" - nobody can do that for you.
As mothers with varying schedules, there are times when that 4% of our day requires us to rest our bodies, recharge, take care of others, fix dinner, etc., etc., etc. YOU make the choice as to whether what you need to do is an excuse or a legitimate need and you don't have to justify that to anyone. Only yourselves.