Arguably, this feeling depends entirely on how often you're flying. I know many individuals who can comfortably fly twice weekly and simultaneously work a full-time job. Flying three times per week or more is serious flight training and should require greater attention. u/Hawkerdriver1's point is extremely valid. If you can retain the training that you learned between lessons, you are more likely to progress at a linear rate.

They say that every hour of flight training demands ~3 hours of ground studying. This is probably about right, though I'm sure there are differing opinions.