Personally, spiritual capacity is the degree to which you understand who you are and what you want most.
Oh? How did you arrive at this idea?
God, our holy Maker, says to us in His word, the Bible, that He made us to be vessels for His use, temples in whom His Spirit dwells, joint-heirs with His Son, Jesus Christ (among other things). (
2 Ti. 2:21; 1 Cor. 3:16; 6:19-20; Ro. 8:16). He also says to us in the Bible that the best way for us to live is in death to ourselves (
Matt. 16:24-25, Jn. 12:24-25), denying what we want for the sake of God and others. God has a very different view of things than you, eh?
Building your spiritual capacity is a journey of self-discovery; it means taking time to understand your motivations and what makes you happy.
I'm on this journey.
How do you know any of this?
Happiness is actually among the least valuable and important things in life. Justice, mercy, peace, freedom, love, integrity, courage - these are all far more noble and necessary things than happiness, often requiring the sacrifice of happiness to obtain and maintain. And if they aren't, it becomes extremely difficult ever to be happy. Just ask folks in North Korea.
You know, God says in His word, that there's nothing good in us (
Ro. 7:18; Ro. 3:10, 23; Tit. 3:3; Eph. 2:1-3). This is why we need to be saved from ourselves, from God's wrathful judgment of our sin, and and given new spiritual life by God through Jesus. All other paths, the Bible says, lead ultimately to darkness and eternal punishment.