How do we maintain a high level of motivation?

When we decide to do something, we have high motivation. Then, How to maintain a high level of motivation is a problem

I searched online and got some tips.

Squash negative thoughts and replace them with positive ones. This is one of the most important motivation skills, and it is important to practice it daily. It’s important to start monitoring your thoughts, and to recognize negative self-talk. Just spend a few days becoming aware of every negative thought. Then, after a few days, try squashing those negative thoughts like a bug, and then replacing them with a corresponding positive thought. Squash, “This is too hard!” and replace it with, “I can do this! If that wimp on TV can do it, so can I!” It sounds corny, but it works. Really.

Stay accountable. If you've committed yourself publicly, through an online forum (try wikiHow's Chat Forum!), on a blog, in email, or in person, stay accountable to that group of people. Commit to report back to them daily, or something like that, and stick to it! That accountability will help you to want to do well, because you don’t want to report that you’ve failed.
I like this one. I used to walk for an hour each day as a kind of exercise. Sometimes I do want to quit with different kind of excuses, such as weather, housework,etc.  After I downloaded a app, I have to share my record with my friends, and they also supervise me daily. This is really an effective way to keep doing something. We should make best use of social media nowadays.

Think about the benefits. Thinking about how hard something is is a big problem for most people. Waking early sounds so hard! Just thinking about it makes you tired. But instead of thinking about how hard something is, think about what you will get out of it. For example, instead of thinking about how hard it is to wake early, focus on how good you’ll feel when you’re done, and how your day will be so much better. The benefits of something will help energize you.
What do you think of this tip?When I keep on diet, I force myself to go shopping. When I see those beautiful clothes and amazing models, I know that I can get benefit from being thin.

Find like-minded friends. Staying motivated on your own is tough. But if you find someone with similar goals (running, dieting, finances, etc.), see if they’d like to partner with you. Or partner with your spouse, sibling or best friend on whatever goals they’re trying to achieve. You don’t have to be going after the same goals — as long as you are both pushing and encouraging each other to succeed. Other good options are groups in your area (be part of a running club, for example) or online forums where you can find people to talk to about your goals.

Read inspiring stories. Inspiration can come from others who have achieved what you want to achieve, or who are currently doing it. Read other blogs, books, magazines. Google your goal, and read success stories. You will soon grow to love reading success stories.
For me, I generally read some successful stories about new immigrants, which stimulate me to work harder and harder to realize my dream.

Get help. It’s hard to accomplish something alone. Whether it's quitting smoking, running a marathon or writing a thesis, it is important to find your support network, either in the real world or online, or both.

We all need friends, who can help us when we are in trouble or when we are depressed.

Reference
How to sustain motivation When you are struggling   retrieved from http://www.wikihow.com/Sustain-Motivation-when-You%27re-Struggling