Thai forest monk Thanissaro Bhikkhu describes that which never disappoints.
ACCORDING TO THE BUDDHA, there is one thing that doesn't disappoint. When you pursue Awakening, it's not going to lead to disappointment. Quite the contrary, it goes wildly beyond your expectations, wildly beyond your hopes. Even just the first taste of the Deathless, stream entry, is enough to produce a seismic shift in your whole awareness, your whole understanding of what you think you are and what's possible in life, and in the importance of your own actions. Once you reach that state, your conviction in the Buddha, the Dhamma, and the Sangha is unshakeable. Your standards for what counts as true happiness get ratcheted up immeasurably.
But in the meantime, until you reach that state, you're going to have shakable conviction. It's part of the game. It's only to be expected because you haven't seen the results really turn into something earthshaking yet. This is why you have to work at your sense of conviction. Your drive for true happiness—your belief that such a thing is possible—is what's going to see you over the hurdles placed in your way.
Like someone lost in the forest, if you're not really convinced that there's a way out, you give up very easily. You run into a thicket here, a steep cliff there, and it just seems way too much. But if you're convinced there's got to be a way out, you've heard of other people who've made their way out, you think, "It's got to be in here someplace." You keep looking, looking, looking. And finally you see how the other people made their way out: "Oh. That was the path they took."