Injuries suck. The worst part isn't the pain caused by the injury, but the ongoing psychological withdrawal from exercise.
Luckily, there is a way to minimise the strength losses caused by a single limb injury.
A large percentage of the strength in a limb isn't caused by muscle size (cross-sectional area), but by neural factors - that is, the nerve telling the muscle fibres what to do in efficient and coordinated ways.
The cool thing is, you can continue to train the neural patterns of an injured limb even if you're not using it. This is called 'cross-education'. Cross-education refers to the fact that if you have an injured arm or leg, by training THE OTHER arm/leg, you are maintaining the neural patterning in the injured arm. So even though you may lose some muscle, your movement patterns are maintained, and strength losses are minimised. So drag out those kettle-bells and dumbbells and start working the good limb.
You can also use injuries as an opportunity to work on your weaknesses. I'm reminded of a story told by legendary Australian Swim Coach Laurie Lawrence. He told of one of his charges, Duncan Armstrong. Duncan broke his arm. Laurie put a garbage bag over the cast and threw him in the dive pool. Duncan kicked, vertically, with his arm held over his head for two hours every session. Duncan went on to win gold in the 200m freestyle in the Seoul Olympics. He attributed the win to his legs. His kick got him over the line.
What's your excuse?