Good suggestion from Seija.

When you make the edges softer, you can make the focalpoint more clear.

Like John Lovett does here.

John uses gesso for this.

But you can also do it more subtle by making more details in the focal area.

Or make the tree a focal point if you kept it light/white.

Make a sketch at forehand. You can judge on the values how successful your painting will, or can be.