Our Speaker during Family Bible Hour was Mr Steve Witter.  How do we fulfill and face the impossible(s) in our lives, and do what Paul's reminds  us to do?:
...walk worthy of the Lord unto all pleasing, being fruitful in every good work, and increasing in the knowledge of God; Strengthened with all might, according to his glorious power, unto all patience and longsuffering with joyfulness;  ~ Colossians 1: 10, 11

The answer to the questions may be found in the life of Joshua, as we look at the passage of  his "impossible" situation as he faced the swollen Jordan River (see Joshua 3: 5-17):

And Joshua said unto the people, Sanctify yourselves: for to morrow the Lord will do wonders among you...And the Lord said unto Joshua, This day will I begin to magnify thee in the sight of all Israel, they they may know that, as I was with Moses, so I will be with thee.  And thou shalt command the priests that bear the ark of the covenant, saying, When ye are come to the brink of the water of Jordan, ye shall stand still in Jordan.  And Joshua said unto the children of Israel, Come hither, and hear the words of the Lord your God.  And Joshua said, Hereby ye shall know that the living God is among you, and that he will without fail drive out from before you the  Canaanites, and the Hittites, and the Hivites, and the Perizzites, and the Girgashites, and the Amorites, and the Jebusites.  Behold, the ark of the covenant, even the Lord of all the earth passeth over before you into Jordan.  Now therefore take ye twelve men out of the tribes of Israel, out of every tribe a man.  And it shall come to pass, as soon as the soles of the feet of the priests that bear the ark of the Lord, the Lord of all the earth, shall rest in the waters of Jordan, that the waters of Jordan shall be cut off from the waters that come down from above; and they shall stand upon a heap. 

According to the passage above, there are three requirements in order for a person to fulfill his/her calling from the Lord and to face all humanly-impossible situations in life:

1. Sanctification.  Do I know the Lord? If not, I have no hope nor help to begin with. If yes, am I set apart for the Lord?  Have I made the choice to follow Him and no other?  Am I holy as He is holy? 
2. Saturation.  I must spend time being saturated in God's Word.  Jesus said in John 8:31 "...If ye continue in my word, then are ye my disciples indeed."   
3. Submission.  I must make the choice to obey God.  Hebrews 11 is the honor roll of people who had made the difficult choice of obeying God in spite of very difficult or impossible situations.

Lastly, Mr Witter reminds us to have "stones of remembrance" as Joshua encouraged the people to have in Joshua 4: 1-7.  For us as Christians, these would be: following the Lord in Baptism by immersion; and doing what the Lord Jesus asked us to do by being present and participating in the Lord's Supper.