You'll always desire the results you want. If I said we could do a 3 hour training session today and you'd wake up tomorrow feeling and looking exactly as you wanted, you'd do it right?
So motivation isn't what's missing.
But saying your motivation has dropped or you've lost it stops you from actually doing what you should be doing.
There are 3 areas to master when it comes to this.
Accountability, A Workable Plan, and Patience
Most people are terrible at personal accountability, these are the times when no one is watching. What you do during these times goes a long way to determining your progress. But having an accountability coach can be a game changer. If you know someone is looking, or will be checking in you're far more likely to stick to your plan.
A Workable Plan
That plan must be a workable plan though. Most attempts at improving one's health and fitness revolve around a) avoiding any foods that are considered bad for you and b) excessive time spent exercising, yes too much exercise can be a bad thing!
Any plan you decide to implement either with the help of a coach or by yourself should account for life getting in the way. There will be social events, there will be busy days and stressful days so having a plan that's simple to stick to during these times is imperative for your long term success. For example at SF we've helped people lose weight and improve their health while eating crisps everyday, or without giving up alcohol, or with 'only' exercising 3 days a week.
Plans like these ensure you'll stick with it and there's no falling off the proverbial wagon. In fact, there is no wagon with a workable plan.
Now, plans like these may not show ultra fast results. But remember, when someone goes on a highly restrictive plan they can often only stick with it for a few weeks. And when they stop they lose any progress they have made. So having patience is key to sustainable results. Give yourself longer to achieve the results you want and celebrate any and all progress, no matter how small it may seem.
I'm always amazed at people's reactions to 'only' losing a pound. They rarely celebrate it, instead berating themselves for not doing enough. But do that every week for a year and they'd be nearly 4 stone lighter and remarkably healthier. Same goes for lifting weights every little bit of progress, whether it's an extra repetition or a slight increase in weight should be celebrated. Because it's only by making this consistent progress that you'll end up changing your health & fitness for good.