When writing you shouldn't just stop at the end. Instead, you should try to make the ending memorable as it is then likely to stay in your reader’s mind.
There are many different ways of doing this. If you are writing a ghost story, you can leave the reader in a state of suspense, unsure and open, as if something might happen next. Like this:
He turned away just as a shadow rose up from the bricks. Was it a trick of the light? Or something else?
In other writing, you normally need to come to a definite conclusion, something like this:
Once the trees are chopped down and the play equipment bulldozed away, it will be too late. Too late to save our park. Too late to think about our children. And too late to remember those who died for our freedom. So act now to safeguard this valuable, beautiful area for the future.
If you get it wrong, it can seem silly, like these examples:
Once the trees are chopped down and the play equipment bulldozed away it will be too late. Act now to safeguard this valuable, beautiful area for the future. But remember that it could still be a car park, and create jobs for our community. Think about it - are you sure? I certainly don't know what to think.
Once the trees are chopped down and the play equipment bulldozed away - well who knows, really. It's one of those things, and who can blame anyone.
In the first example, the person isn't sure what point they are making and what they want to achieve - so how can they convince anyone else? In the second, the argument has just fizzled away... there is no more detail. Make sure you don't waffle or end vaguely.