Your mind is the most powerful thing God has Gifted you with and it is used in correct way you have the Universe with you.
Man's word is Spirit in man. Spoken words are sounds occasioned by the vibration of thoughts, thoughts are vibration sent by ego or by the soul vibration.
A man's words are lifeless if he fails to impregnate them with spiritual force. Talkativeness, exaggeration or falsehood makes your words as ineffective as paper bullets shot from a toy gun. The speech and prayers of garrulous or inaccurate persons are unlikely to produce beneficial changes in the order of things. Man's words should represent not only truth but also his definite understanding and realization. Speech without soul force is like husks without corn.
Words saturated with sincerity, conviction, faith and intuition are like highly explosive vibration sounds which set off, shatter the rocks of difficulties and create the change desired. Avoid speaking unpleasant words, even if true. Sincere words of affirmation repeated understandingly, feelingly and willingly are sure to move the Omnipresent Cosmic Vibratory Force to render aid in your difficulty. Appeal to that Power with infinite confidence casting out all doubt, otherwise the arrow of your attention will be deflected from its mark.
After you have sown in the soil of Cosmic Consciousness your vibratory prayer - seed, do not pluck it out frequently to see whether or not it has germinated. Give the divine forces a chance to work uninterruptedly.
The above is a beautiful explanation given on affirmations by beloved Guru Parmahansa Yogananda Ji
Some Affirmations that you can practice are given below:
Repeat these Affirmations daily and say as much u can. Feel them while saying them.