Push yourself to do it. You must not do everything but doing a little might encourage your way further.
If you want to overcome motivation at work, you need to create some interest. Allow yourself to learn new ways of approaching your tasks. Concentrate on your gain after finishing the work fast instead of worrying about how you can carry out the task.
Sometimes, the knowledge that we need some encouragement is just enough to get ourselves motivated. Enthusiasm is gotten from the ability to cherish.
Adjust the way you approach things or your whole time schedules. For examples, waking up early in the morning gives me more inspiration to accomplish my writing. But when I started becoming less enthusiastic, I change my routine from early to bed-early to raise to late to bed-late to night. In summary, I do most of my inspirational writings late in the night and overtime, switch to morning again.
So the most important thing about overcoming lack of motivation is to know your time and how to use it for your benefit, regardless of the challenges.
Do not compare yourself with others. You might end up dreaming someone's dream. Read yourself, but always do things in favour of your own enthusiasm. You are free to switch if things aren't working fine.
We have big abilities but sometimes we need to understand our limits. Learn new skills. Having various ways of doing things always give you some motivation.
To overcome lack of motivation you also need to overcome fears. Those fears that have no root let alone fruits. Recall your past achievements and how you stay motivated to get things done.
Be prepared for challenges, for they come through different channels. Even though you fail, there's every chance to do better. Stay optimistic.