Training is somewhat of a double-edged sword by that I mean that to become your strongest, you will encounter mundane and monotonous periods of training. If your training is simply for health benefits then training, which consists of a large variety of exercises, movements and activities will be sufficient. But training for optimal performance involves very specific training.
This is because adaptations are specific to the type of stimulus provided. To put it simply, one cannot hope to become a great squatter employing long-distance running. To become a great squatter, then the squat movement must be practised often and with a heavy load. So its perfectly normal to go through, let's say stale periods of training where motivation is low and progress non-existent. The question is, what you should do once you encounter yourself becoming a little stale?
My advice would be to spend four weeks, focusing on a different aspect of your training.
For example, if you are a powerlifter spend four weeks training like a strongman. If you are a weightlifter, then switch to dumbbell only workouts. You could spend four weeks doing only bodybuilding type training or do circuit training to work on your conditioning. The options are endless; the change in training style will keep things fresh due to the new exercises or training style. This four week period is often met with apprehension though as it seems to take the lifter off the beaten path, they fear they will lose all their strength. I will say this; however, no powerlifter has become worse by improving his grip strength as a result of strongman style training. And no Weightlifter lowered his or her total due to better anti-lateral flexion strength as a result of dumbbell training.
My point is that a four weeks period isn't enough to reduce or lose strength. Sure you peak for competition exercise might drop slightly but as soon as you return this will very quickly return. So don't be afraid to adjust things for a month.
Another reason for finding yourself stale is when you focus too much on the result and forget about the process. Strength is the result of hard effort over a long period of time. Athletes are not developed overnight, and coaches cannot create miracles by cutting corners. To improve this, a shift in the mindset can really help, just because every session isn't a new personal best doesn't mean it wasn't productive; every session is work in the bank.
Wrapping things up.
Don't be afraid of a little change for a few weeks to keeps things fresh for you. And remember training has ups and downs you know the old saying if it were easy everyone would do it!