Many times during a match you will be faced with a decision on whether to go for the winner or just make sure you get the ball back in play—or at least it seems like that. However, there are many other options besides these two obvious ideas.
My thought is to play the shot like you would play it if this were the first point of the match; this basically means do what you normally do. There are ways to make your aggressive play a bit safer and also ways to get your consistent idea to make it tough on your opponent. If you decide to go for a winner or big shot, hit the ball aggressively to a big area of the court rather than close to the lines. Hit the shot hard but with a little additional spin to help control the depth and direction.
You can also play more consistently and still get your opponent in trouble by using placement, shot variation, and extra spin. If you are an aggressive player, think more about playing the point somewhat on the aggressive end. In contrast, if you are a consistent player, think more about playing the point more towards the consistent idea. Going to one extreme or another (going for a winner or just getting it in) is not the best thought process when you are playing.
Focus on doing the basics well (like serving and returning serve) and play the rest of the point like you would play the first point of the match, or how you would like to play most of the points in the match.