On this the gemara comments,הַבֹּטְחִים בה'-- כְּהַר-צִיּוֹן לֹא-יִמּוֹט, לְעוֹלָם יֵשֵׁב."Those who have faith in Hashem are like Har Tzion, which cannot be moved, but abide forever."
"Just as Hashem promises to rebuild Har Tzion, so too will Hashem return the houses of the righteous (that were destroyed)."On this point Rav Kook (Ein Ayah Berachot Vol II, p. writes,
Bitachon is limited [only to the point] that we complete our efforts to the best of our abilities. That which our hands cannot reach - there is the place for Bitachon. For the place which our ablilies reveal, God forbid that we should use our Bitachon, for this isn't Bitachon, but instead foolishness and insolence towards Heaven."I'm pretty sure that Rav Kook was talking about building the Land of Israel, and especially those who rejected Jews physically building the Land, instead insisting that we wait for a miraculous redemption. Yet, the message also applies to all aspects of our lives. God doesn't want to have Bitachon first. He wants us to act - to do our part, to the best of our abilities. After we've done that, then we turn to God with faith.
Then it's all up to Him.