How do you measure how strong your faith is? By whose standard? What does he mean by faith? Faith in what? These are difficult questions to answer.
I am a Committed Christian, so have faith in God through Jesus and I was baptized at 41 years of age by total immersion (which was scary for me, as a non swimmer!) Not that I had to swim, mind you! But I didn't like going under water. However, on the day, I was filled with peace when I did it and joy afterwards. I have attended a Baptist Church regularly, ever since.
I am quite certain that I will never turn away from my Christian belief, so does that make it strong? I think it is a firm belief.
However, I would not scream about it on street corners, like some do. Those people make me feel uncomfortable. I don't feel that is what I am supposed to be doing at all. If people ask me, I tell them what I believe, but I don't ram it down people's throats. So does that make my faith weak?
To me, being a Christian means having a personal relationship with God through prayer. I have certainly come through some difficult times in my life and have felt that I've been helped by the power of prayer many times.
Some times things get in the way of prayer, like blogging! So I will use this post as a little testimony (groan from lots of people, I expect, but I won't do it frequently!) and I will give something back to God, so it is tit for tat!
Could it be David meant faith in Human Nature? This is a bit of a risky thing, as people can let you down. Even the best of friends can do that, though admittedly, there are some wonderful people about. I'd sooner put my complete faith in God, though humans are important to me.
Faith in myself? Well, everyone needs to have some faith in themselves or else they could never cross a busy road, but I would not like to think that everything depended on me and there was nothing else! I suppose some people who don't believe in God, must be very strong people, going it alone. But what happens after death? Just suppose they got it wrong?
Some people put their faith in luck and charms and things, but that is not for me!
So who am I to judge other people or myself? I will trust God to sort it out and continue to put my trust in Him and believe on Jesus for everlasting life!