Using this is taking previous data points and attempting to predict the future, which can bring errors because the past is never indicative of future progression. Of course if the company is doing well it is likely the company could continue doing well, but there is no guarantee.
When forecasting, there are several items you need to take a look at, with the first being sales. You should be looking at the company and see if sales are going to continue on their current trend. If they do not sell products, be sure to look at revenue and ensure that is steady or going up.
Secondly, you want to look at the executive management and find out if they are aligned with your beliefs of where the company should be headed. Management is key in these companies because they are the ones that decide where the company heads and if they can compete.
Lastly, take a look at the technical indicators and see how they line up for the future. Of course the chart leaves out some of the fundamental data, but you need to incorporate all aspects of research to help give you a well rounded opinion.
Time series forecast may not be for everyone but it is certainly a way to help predict the future using a potentially nice chart. Be sure to test the forecasting and use it on a demo account first because you do not want to risk your hard earned money. Join an investing community and bounce ideas off of them and if you are still stuck, consult an investing professional and they can help to point you in the right direction.