Maintain the positive thought under all circumstances. Whatever thoughts are concentrated upon, those thoughts become powerful. It is like the growth of a seed.
When a thought, a positive thought, is planted in the mind and it is concentrated upon, it becomes like sunlight adding energy.
The more the concentration on them these thoughts begin to grow.
It works other way as well. All negative thoughts consistently pollute your mind and moving to mental darkness. Avoid all negativity and convert your pessimist feelings to the positive energies. This is practically doable. All that matters is how much you want to tune your mind to make this happen. It takes a while to practice this but empowers your brain powers by ten folds.