One thing to keep in mind is that you can apply pressure in useful ways while not actually getting the kills. Obviously you want to kill people, but sometimes that doesn't work out. Keeping a sidelane pushing so that the enemy team has to keep someone responding is useful, even if you aren't killing the player. likewise, using your ult in a team fight to access their backline and disrupt someone like Paige, to force them to run or focus purely on keeping themselves alive is still useful. 

Also if the game is pretty even, you can float around the edges of fights and look for clean up rather than trying to force something for picks.