What can I do when I am overcome with fear? How do I find the strength to go on?

Psalm 46:1-2
God is our refuge and strength, a very present help in trouble. [2] Therefore will not we fear, though the earth be removed, and though the mountains be carried into the midst of the sea;

John 14:27
Peace I leave with you, my peace I give unto you: not as the world giveth, give I unto you. Let not your heart be troubled, neither let it be afraid.
God promises to comfort us in our fear if we seek him when we are afraid. We have the confident assurance that he is with us in any circumstance.

Deuteronomy 31:6
Be strong and of a good courage, fear not, nor be afraid of them: for the LORD thy God, he it is that doth go with thee; he will not fail thee, nor forsake thee.
Remind yourself that God is always with you. Your situation may be genuinely threatening, but God has not abandoned you, and he promises to stay with you. Even if your situation is so bad that it causes death, God has not left you but has instead ushered you into his very presence.

Ephesians 1:3
Blessed be the God and Father of our Lord Jesus Christ, who hath blessed us with all spiritual blessings in heavenly places in Christ:
Remind yourself that no enemy or adversity can take away your most important blessings—the forgiveness God gave you for your sins, your relationship with him, and your eternal salvation. These remain secure even when your world falls apart.

Revelation 22:5
And there shall be no night there; and they need no candle, neither light of the sun; for the Lord God giveth them light: and they shall reign for ever and ever.
Remind yourself that as a Christian, your destiny is victory! Present hardships and heartaches are temporary. You can go forward with the confidence that you are on the winning side.

Philippians 4:6-7
Be careful for nothing; but in every thing by prayer and supplication with thanksgiving let your requests be made known unto God. [7] And the peace of God, which passeth all understanding, shall keep your hearts and minds through Christ Jesus.
Pray with a thankful heart, asking God to give you what you need to deal with your fear. Peace is not the absence of fear but the conquest of fear. Peace is not running away but overcoming.

2 Timothy 1:7
For God hath not given us the spirit of fear; but of power, and of love, and of a sound mind.
Fear presents an opportunity for you to develop greater faith as you call upon the power of God to help you.

Genesis 26:7
And the men of the place asked him of his wife; and he said, She is my sister: for he feared to say, She is my wife; lest, said he, the men of the place should kill me for Rebekah; because she was fair to look upon.

Joshua 17:16
And the children of Joseph said, The hill is not enough for us: and all the Canaanites that dwell in the land of the valley have chariots of iron, both they who are of Beth–shean and her towns, and they who are of the valley of Jezreel.
Fear must not keep you from doing the things you know are right. You are not meant to live in fear.