Staying gym motivated is probably one of the hardest things to do when you've got a busy lifestyle, especially when it comes to Summer where the nights are longer and your friends are meeting up for mid-week drinks. No matter how many times you've said 'I'll do it tomorrow' sometimes that day takes a whole lot of days to come round - but it's fine. Everyone has dips in motivation, it's just how you combat it that will make you stand out from the rest.
Mix up your training plan
Have you hit a wall when it's comes to training? Has that circuit got to easy, or are you sick of seeing the same scenery on your run? This is the problem I tend to have. I go through phases of how I like to train, for months I'll stick to gym classes (a variety of), then the next few months I'll do my own training, then I'll become bored of the gym all together and do long distance running, then I'll get bored of that and have PT sessions... Then I'll go right back to the beginning. Currently I'm back on gym classes which has seemed to get my motivation back. I like training alongside other people sometimes, it really spurs me on.
If you're becoming bored and feeling less motivated to hit the gym or a local park, then swap your training around and try something new. Joining a running club could help or even changing to personal training sessions. Try something new and exciting, you'll focus your efforts a lot more and challenge your body in a different way which in actually fact will give you new results.
Learning what's right for your body
I've recently learnt that not everybody can train 5-6 times a week - that doesn't make you a lesser person than the women stood next to you who does. People have different priorities, they work different patterns and they have different social lives. Don't let this demotivate you. Do what you can and be proud of what you achieve, no matter how small or insignificant you might think it is.