Its very rare that a goal orientated person, like most athletes are, is going to be 'too lazy'. However, even the most dedicated athlete is tested when its raining hard, its cold, or they get home from work late.

Get good at questioning yourself: just ask the question "Am I looking for a reason not to train?" A good approach is to ask with the long term goal in mind - "what's the best thing I can do now to help me achieve X?" Sometimes, its better to rest - even if your lack of motivation is from a need to take a mental rest (often the case after a hard days work).

Another good strategy is to promise that you will start the session, do the warm up and then make a decision. But, DO give yourself permission to make a TRUE decision - and not beat yourself up if 10 minutes in you know its not going to happen.

Often, just really listening to what our body is asking of us is the best practice.