Mind is like a magnet so don't use it inappropriately

lets see how our mind could harm us by one fictional story. Tom was living in non native English speaking country, but he wants to speaks English fluently like natives, so he started practicing English speaking, and he was very sincere, and consistent during whole process, and he assumed next year he would reach his goal, but he couldn't became a fluent English speaker. You know why because tom was a gloomy person, and he has developed habit of saying negative words for himself like my English is terrible, and I will be doing fumble during conversation, and at the end of the day his English becomes terrible, so instead of using negative words for yourself. We should start appreciate our efforts because no one knows the consequences, but when you will appreciate your effort, and become optimistic then whatever goal you have that will become easy for you.