Remember that spark of excitement when you where young? When we believed that nothing was impossible. We believed we could explore space, be president, invent the cure for cancer - we could do anything.
It reminds me of the scripture in Genesis 11:6b where God said:
...Behold, the people is one, and they have all one language; and this they begin to do : and now nothing will be restrained from them, which they have imagined to do
God says there is much power in the imagination/dreams of men - so much so that he found it prudent, at that time, to separate men by dividing their languages.
If, as God says, we can do anything that we imagine, why don't we? I believe that lies creep in and we accept them to protect our fragile egos from disappointments, hurts, failures and rejections. These lies prevent us from trying again and take the place of those God-planted-dreams and imaginations.
Those lies (you can't do that, you are a failure, that won't work, no one will support you, no one will listen to you, no one wants to hear you, you aren't good enough, you'll just screw it up) beat us down to keep us from trying and limit what God can do through us and also the plan he has for our lives. Do those lies sound familiar? They sound to me like the same sort of things an abusive spouse or parent might tell an abused person to keep them under their control.
The enemy, like an abuser, would like to keep you isolated and convinced that you cannot do what God has created you to do - that you are not able to carry out the plan he has for your life.
But God says, do not listen to the enemy - not in our own stregth, but in God's strength and might. Trust in him, lean on him. Isaiah 40:28 - 31:
Have you not known? Have you not heard?The Lord is the everlasting God, the Creator of the ends of the earth.He does not faint or grow weary; his understanding is unsearchable.29 He gives power to the faint, and to him who has no might he increases strength.30 Even youths shall faint and be weary, and young men shall fall exhausted;31 but they who wait for the Lord shall renew their strength; they shall mount up with wings like eagles;they shall run and not be weary; they shall walk and not faint.