"Be impressed by intensity, not volume." -Greg Glassman
The workouts that we write are designed to create a specific stimulus from the training. In the sport of CrossFit, we program for the best athletes in the gym, and then scaled based off of your abilities for you to achieve an appropriate response! If the workout is scaled it doesn't make you LESS of a person or athlete, it just means your fitness level is different from others in the box. Many times the hardest thing to do is control our ego. If you scale the workout appropriately you'll get a better response and progress much faster. You should never scale to make the workout "easier", always scale to your ability. A long-term goal of scaling is creating the ability to perform workouts "Rx".
That being said, sometimes the scale of the workout is a time cap. It is OKAY if you time out of a workout. When we put a time cap it was discussed and decided that we didn't want you working on those movements for say, longer than 12 minutes. Or we wanted you to scale the weight or movements appropriately enough so that you can finish the workout within that time cap and bring the intensity that is desired for a workout. This means the intensity is higher and the response from the stimulus will be appropriate.
A few weeks back, I attended the CrossFit Games Mid-Atlantic Regional competition. There was a workout where 40 men competed, and only a handful of them finished it. These are the best male athletes in the region or even world and only a few men finished the workout, the rest timed out- so, don't be discouraged or allow self-doubt to creep up on you next time you are capped.
To get the best response out of your workouts, discuss with your coach an appropriate scale and your physical response will be better. For more in depth information, check out this CrossFit Journal article.