The hardest part of a workout is often getting through the door. On certain days, it feels like a constant battle with that inner voice. "Don't go", " You've had a long day", "Why not go tomorrow?".
Now if you really don't feel like training, another rest day can actually be productive. Otherwise, don't give in to those voices!
The best thing you can do in this situation is to simply show up. I appreciate that this is easier said than done. However, try and break down your journey to the gym and the start of your workout, into small chunks.
Make sure you leave your kit in the car. Don't go home after work. You'll find other jobs you need to do, or the lure of the sofa may be too much! In a situation where you really don't fancy training, try not to think about the workout at hand. Get to the gym and get warmed-up. Don't focus on anything apart from this. Then move on to your first exercise. By this time, the hard work is done. You will no doubt be in full swing before you know it. If you are having an 'off day', simply adjust the intensity of your workout. You are better off doing a slightly easier workout and maintaining that habit of showing up. Remember, every session counts.
The same applies in the morning. This gets increasingly more difficult when it's dark. If you are planning to wake up early for a workout before the start of your day, it is very easy to hit the snooze button instead. This is when you have to be strong! Again, break it down into chunks. Get up, get ready, go, warm-up, train! Get everything prepped the night before. Not having to think too much is always a bonus in the morning, allowing you to concentrate on the job at hand.
See you in the gym :)