I heard that so many times from my circle of Buddhist acquaintances but it's not true.

If Jesus is merely a prophet, he would have said so.

But He have not reveal Himself as just a prophet.

In Fact He have said very clearly in
John 10:30 (NIV)
I and the Father are one. 
Meaning He is God.

Because they are blinded by the god of this world. They received not the Truth

It's not only them but all other religion has this similar doctrine that Man finds appealing.

Self Glory.

I want to earn my own Salvation my way, that's the world's religion.

Christianity is about God's way.

Depending on God who is most the powerful being for our life.

That is the most wisest decision anyone can make in their life.

God Bless.

It really depends on how we judge our standing with God.

there's usually 2 scenario.

1) If you judge based on external circumstances of what happened or how much you have done for God in order for God to love you then it will be up and down as you said.

But

2) If you judge based on what He says about you, irregardless of circumstances or whether you have done anything or not, then your Faith can be more secure.
Sometimes our Faith need to ignore circumstance but to just Believe. Believe first, understanding WILL come later. God never leave his children. That is stubborn Faith, and a good one.

And this is what he says in;
Jeremiah 31:3
The LORD appeared to us in the past, saying: "I have loved you with an everlasting love; I have drawn you with unfailing kindness.

Everlasting = everlasting, forever.
Hosea 11:4
I led them with cords of human kindness, with ties of love. To them I was like one who lifts a little child to the cheek, and I bent down to feed them.

Like a loving Father to his own child.

John 6:37
All those the Father gives me will come to me, and whoever comes to me I will never drive away.

God will never ask you to go away when you come to him.
ALL these are based on his Love for you. If God don't love you, He will never declare this in the scripture.

When you have strong affirmation , knowing that God loves you, your Faith will work effortlessly. You don't need to conjure up Faith.