When training for strength, you automatically increase your capacity for muscular endurance. Your muscles will only grow as thick as needed to cope with the resistance you make them use. Babe Ruth struck out 1,330 times, but he kept swinging the bat and hit 714 home runs. He did not let the strikeouts bother him. He kept swinging.
People only remember the home runs.
You will have many workouts where you cannot increase your poundages. But you don't quit. You keep at it. You learn about how to cycle your training intensity. You learn how to avoid going stale.