In many instances, our mind tells us to hit the shot faster to win the point in a tennis match.
This can be very effective if you have a particular shot that is a weapon. However, there are many different ways to win the point once you get the opponent in trouble.
Taking some speed off the shot by hitting more topspin or increasing the height over the net can often throw off the other player's timing. Hitting a slice after you have hit a few topspin or flat balls can also produce a timing error. Changing the direction of the shot is another way to win the point. Sometimes moving forward and hitting your shots from an area between the baseline and the service line can be very effective since the ball will get back to the opponent sooner, even if it is hit at the same speed as the previous shot. Hitting a shot shorter and angled after hitting a few deep solid balls can also make it extremely difficult for the player on the other side of the net.
Finally, coming in to the net and finishing the point with a well directed volley can put a tremendous amount of pressure on the opponent and cause some additional errors later in the match.
There are many strategies, other than just hitting the ball harder, that will work very well in a match situation. Find something that works and don't be afraid to use your regular speed on the shot that finishes the point.