Does everything - everything in our heart and every external event- happen according to God's plan? (Catholic) I think everything - everything that takes place in our hearts, and everything that takes place externally - happens so according to God's plan. I don't think my opinion conflicts with our free will.

The catechism teaches that God's plan requires cooperation of his free creations, but it also teaches that "all are laid bare before his eyes, even the things that are yet to come to existence through the free action of his creatures". 

I think that God had incorporated all our free actions and decisions (which we are responsible for) into his plan from the very beginning. Like, even Judas' betrayal was a part of God's plan (he clearly foresaw that Judas will betray Jesus from the beginning; and he permitted it to happen in keeping with his plan. It is Judas own downfall and it was his own decision that he will betray Jesus, but God incorporated this Judas' free will into his plan).

If something - however tiny or insignificant it can be - can happen unexpectedly outside of God's plan, how can Church be so sure that our final ultimate end will be achieved?

So my question is:
Is it correct to say that "everything - everything that takes place in our hearts and mind, and everything that takes place in external world - happens according to God's plan"?

Please answer according to Catholicism.
Everything is subject to God's providence, but that does not imply God necessitates everything to happen the way it does.
St. Thomas Aquinas, in his Summa Theologica I q. 22 a. 4 article &quot;Whether providence imposes any necessity on things foreseen?,&quot; answers:

Divine providence imposes necessity upon some things; not upon all, as some formerly believed. For to providence it belongs to order things towards an end. Now after the divine goodness, which is an extrinsic end to all things, the principal good in things themselves is the perfection of the universe; which would not be, were not all grades of being found in things. Whence it pertains to divine providence to produce every grade of being. And thus it has prepared for some things necessary causes, so that they happen of necessity; for others contingent causes, that they may happen by contingency, according to the nature of their proximate causes.

Thus, God's knowing Judas would betray Him in no way necessitated him to betray Him. Judas's acts of his freewill are contingent causes, not necessary ones.
cf. also Thomist theologian Réginald Garrigou-Lagrange, O.P.'s ProvidenceBut perhaps your question is more: &quot;Does God will/want everything to occur as it actually does?&quot; St. Thomas Aquinas answers this in his Summa Theologica I q. 19 a. 6 question &quot;Whether the will of God is always fulfilled?&quot;:

The will of God must needs always be fulfilled. In proof of which we must consider that since an effect is conformed to the agent according to its form, the rule is the same with agent causes as with formal causes. The rule in forms is this: that although a thing may fall short of any particular form, it cannot fall short of the universal form. For though a thing may fail to be, for example, a man or a living being, yet it cannot fail to be a being. Hence the same must happen in agent causes. Something may fall outside the order of any particular agent cause, but not outside the order of the universal cause; under which all particular causes are included: and if any particular cause fails of its effect, this is because of the hindrance of some other particular cause, which is included in the order of the universal cause. Therefore an effect cannot possibly escape the order of the universal cause. Even in corporeal things this is clearly seen. For it may happen that a star is hindered from producing its effects; yet whatever effect does result, in corporeal things, from this hindrance of a corporeal cause, must be referred through intermediate causes to the universal influence of the first heaven*. Since, then, the will of God is the universal cause of all things, it is impossible that the divine will should not produce its effect. Hence that which seems to depart from the divine will in one order, returns into it in another order; as does the sinner, who by sin falls away from the divine will as much as lies in him, yet falls back into the order of that will, when by its justice he is punished.
*primi caeli or the primum mobile, the first thing God moves

Also, in ibid. ad 2, he states that &quot;everything, in so far as it is good, is willed by God.&quot;