I've been reading a great book called Heaven on Earth. It was written in 1654 by the Puritan, Thomas Brooks. The theme of the book is Christian Assurance - something I'm striving to have more of and am resolved to obtain (making my calling and election sure - 2 Peter 1:10).

In chapter five, there is a great section on weak faith and strong faith. Read what Brooks wrote and be encouraged!

Strong faith and weak faith

In the first place, I shall give some hints concerning strong faith. In the second place, I shall give you some hints concerning weak faith. My design in both is, to keep precious souls from mistaking and fainting. Concerning strong faith, I shall give you these short hints:

(1) The first hint. Strong faith will make a soul resolute in resisting, and happy in conquering the strongest temptations, Heb. 11:3; Dan. 6:10.
(2) The second hint. It will make a man own God, and cleave to God, and hang upon God, in the face of the greatest difficulties and dangers, Rom. 4:18; Ps. 44:16-18. So Job will trust in God though he slay him, Job 13:15-16.
(3) The third hint. It will enable men to prefer Christ's cross before the world's crown, to prefer tortures before deliverance, Heb. 11:3.
(4) The fourth hint. Strong faith will make a soul divinely fearless, and divinely careless; it will make a man live as the child lives in the family, without fear or care, Ps. 23:4; Dan. 3:16. "We are not careful to answer thee, O king; our God whom we serve is able to deliver us, and he will deliver us." Micah 7:7-9.
(5) The fifth hint. Strong faith will make a man cleave to the promise when providence runs cross to the promise, Num. 10:29; 2 Chron. 20:9-11. Ps. 60:6-7. "God hath spoken in his holiness," saith David; "I will rejoice: I will divide Shechem, and mete out the valley of Succoth. Gilead is mine, and Manesseh is mine," etc. Though David was in his banishment, yet his faith accounts all his as if he had all in possession, and that because God had spoken in his holiness. His faith hangs upon the promise, though present providences did run cross to the promise.
(6) The sixth hint. Strong faith will make men comply with those commands that do most cross them in their most desireable comforts, Heb. 11:8-9, and 10:34; Gen. 22.
Now, O precious souls! You are not to argue against your own souls, that surely you have no faith, because your faith doth not lead you forth to such and such noble things. Thou mayest have true faith, though thou hast not so great faith as others of the Lord's worthies have had.
The philosophers say that there are eight degrees of heat: we discern three. Now, if a man should define heat only by the highest degree, then all other degrees will be cast out from being heat. So if a man should define faith only by the highest degrees and operations of it, then that will be denied to be faith that indeed is faith, as I shall presently shew.

In the second place, I shall give you some hints concerning weak faith:
(1) The first hint. A weak faith doth as much justify and as much unite a man to Christ as a strong faith. It gives a man as much title to and interest in Christ as the strongest faith in the world. The babe hath as much interest in the father as he that is of grown years. A weak faith gives a man as good a title to Christ, and all the precious things of eternity, as the strongest faith in the world. A weak hand has receive a pearl as well as the strong hand of a giant. Faith is a receiving of Christ, John 1:12.
(2) The second hint. The promises of eternal happiness and blessedness are not made over to the strength of faith, but to the truth of faith; not to the degrees of faith, but to the reality of faith. He that believes shall be saved, though he hath not such a strength of faith as to stop the mouth of lions, as to work miracles, as to remove mountains, as to subdue kingdoms, as to quench the violence of fire, as to resist strong temptations, as to rejoice under great persecutions, Heb. 11:33-35. No man that is saved is saved upon the account of the strength of his faith, but upon the account of the truth of his faith. In the great day, Christ will not bring balances to weigh men's graces, but a touch-stone to try their graces; he will not look so much at the strength as at the truth of their graces.
(3) The third hint. The weakest faith shall grow stronger and stronger. A weak believer shall go on from faith to faith. Christ is the finisher as well as the author of our faith, Rom. 1:17; Heb. 12:2. Christ will use up this blessed babe, and will not suffer it to be strangled in its infancy. He that hath begun a good work will perfect it, Philip. 1:6; 1 Pet. 1:5. Christ is as well bound to look after our graces as he is to look after our souls. Grace is Christ's work, therefore it must prosper in his hand; he is the great builder and repairer of our graces; he will turn thy spark into a flame, thy drop into an ocean, they penny into a pound, thy mite into a million, Mat. 12:20, and 13:32. Therefore do not sit down discouraged because thy faith is weak. That which is sown in weakness, shall rise in power. Thy weak faith shall have a glorious resurrection. Christ will not suffer such a pearl of price to be buried under a clod of earth.
(4) The fourth hint. A little faith is faith, as a spark of fire is fire, a drop of water is water, a little star is a star, a little pearl is a pearl. Verily, thy little faith is a jewel that God doth highly prize and value; and thy little faith will make thee put a higher price upon Christ and grace than upon all the world, Mat. 18:10; 1 Pet. 2:7. Well! remember this, that the least measure of true faith will bring these to salvation, and possess thee of salvation, as well as the greatest measure. A little faith accompanies salvation as well as a great faith, a weak faith as well as a strong. Therefore do not say, O precious soul, that thou hast not that faith that accompanies salvation, because thou hast not such a strong faith, or such and such degrees of faith. A great faith will yield a man a heaven here, a little faith will yield him a heaven hereafter.