How to keep track of the anime you are watching
Anime breaks most trackers for the same handful of reasons — a season is three months and a "season" is also a numbering, films sit inside series, and no two catalogues count the episodes the same way.
Know which season you mean
A broadcast season is winter, spring, summer or autumn. A series season is a numbered block of episodes, and a long-running show can put two of them inside one year. Track the numbered one; the calendar tells you when it airs.
Films are part of the story
A recap film, a sequel film, a side story — several of them continue the series rather than sitting beside it. Keep them in the same list as the series, in the order they happen, or you will meet a plot point you were never shown.
Expect the episode counts to disagree
One catalogue splits a cour into two seasons, another runs the numbering straight through, and a third counts the recaps. Pick the numbering your tracker uses and stay with it; the question that matters is where you stopped, not whose count is correct.
Watch what is airing, not what is finished
A simulcast is the one part of this with a deadline — an episode a week, and a season that ends. Knowing what airs on which day is most of what keeps a running series from becoming a series you dropped by accident.