Always compare your forecast to past results. Look to the past as a reality check. Understand what's changing and why, and what may remain the same. There is a standard way to calculate average growth rates from your forecast or market data. You can use it to calculate monthly or annual growth rates from your forecast numbers.
Most people can see the numbers better in charts.
Particularly with forecasting, in which common sense and judgement are important inputs, make sure to take a good look at your numbers.