1 Thessalonians 5:24 Faithful is he that calleth you, who also will do it.
2 Thessalonians 3:3 But the Lord is faithful, who shall stablish you, and keep you from evil.
Matthew 25:21 & 23 His lord said unto him, Well done, good and faithful servant; thou hast been faithful over a few things,
Do not be confused over the promise of faithfulness, Christ is faithful in all His promises and execution of will. We however are sometimes faithful, as indicated in Matthew 25. The promise is not in us but rather to us.
1 Corinthians 4:4 For I know nothing by myself; yet am I not hereby justified: but he that judgeth me is the Lord.
The answer to the struggle of how faithful we are is in acknowledging that He chooses when to be faithful in using us and we cannot chose that for ourselves. We can be obedient, but faithfulness is not a choice, it is character.
It takes time to build character. The more important the character, the longer it takes to become that character in truth and performance. You cannot fake faithfulness, it is not something you can put on.
Philippians 1:6 Being confident of this very thing, that he which hath begun a good work in you will perform it until the day of Jesus Christ:
You will never catch faithfulness by chasing it.