Taking a break from weight training is actually a necessity. The muscles tear during training and repair during rest periods. What typically happens is that people do not take sufficient rest periods between training and those muscles never fully heal. Taking a week or two off every now and then can help the body fully recover and help yield better results.
In fact, a 2013 study published on the European Journal of Applied Physiology studied 14 men who took a three-week break from weight lifting after consistently training for 24 weeks and found that it had no detrimental effects on their muscles. The research shows how short breaks do not tear down the muscles.
Being gone from the gym over an extended period of time, however, can slow muscle development and cause them to break down. The muscles gradually weaken as the fat rears its ugly head. Use this as motivation to turn things around and get back into a weight training routine.
Getting back into the swing of things takes a little time and patience though. Don't expect to take weeks or months off from the weight lifting routine and be able to jump right back into it. There is such a thing as muscle memory, but it can take as many as six weeks to get back into the heavy lifting if more than a few weeks of training have been missed.
Find a happy medium. Don't go back to the beginning and grab a set of 10-pound dumbbells, but don't go for the 400 pound deadlift either. Start at a weight that is comfortable, yet mildly challenging and work up from there. Treat it much like you did as a beginner. Find the weight of each exercise that you can do at a rate of eight to 12 reps for four to six sets. The last few reps should be difficult. If you have trouble getting five or six reps in, however, it means you need to cut back a little until you are able to rebuild your muscle.
As you ease back into heavy weight lifting and start training regularly again, you will notice faster gains than you experienced before. Your body has already been conditioned to do the work before and it is better able to handle the challenge now.
Sources:
European Journal of Applied PhysiologyHuffington Post