It is actually better to take it slowly. Recovery is the most important part of gaining strength. With most workout routines that people follow, decreasing the number of sets, decreasing the number of reps per set, decreasing the number of exercises (unless you're just doing 3-4) and increasing the number of rest days between workouts will improve results.
Now this doesn't mean you actually have to take it easy. An extensive workout really isn't the best, but an intensive one still can be very good. You increase the intensity by upping the weights. This is taken to the extreme by only doing a single set of an exercise at a weight you can do no more than 10 reps with (6 reps if you have the capacity to do small increments of weight increase, going up to 10 is sometimes necessary if the smallest jump you can make is 10lbs). Depending on the exercise and whether you have a spotter, you'll cheat on the last rep to get it up when you can't do it properly anymore (you've trained to concentric failure), hold the weight up as long as you can (you've trained to isometric failure) and then lower it as slowly as you can (you've trained to eccentric failure). With other exercises rather than cheating to get up you'll just hold the weight at your sticking point for as long as possible, and then slowly lower back down. It isn't really necessary to go for isometric and concentric failure as well, but it will give you some faster gains without having to scale anything else back.