Having all things before you continually doesn’t mean that you always have uniform feelings or that experiences don’t affect you. It doesn’t mean you feel as sad as you can all the time, or as happy as you can all the time. The resurrected Lord felt a fullness of joy with the Nephites:
20 And they arose from the earth, and he said unto them: Blessed are ye because of your faith. And now behold, my joy is full.
21 And when he had said these words, he wept, and the multitude bare record of it, and he took their little children, one by one, and blessed them, and prayed unto the Father for them.
22 And when he had done this he wept again; (3 Nephi 17)
If having all things before you continually meant no variation in one’s feelings, the Lord would not have been able to say his joy was full, and he wouldn’t have wept.
The Lord was upset when he saw the wickedness of the people who rejected Enoch’s ministry:
28 And it came to pass that the God of heaven looked upon the residue of the people, and he wept; and Enoch bore record of it, saying: How is it that the heavens weep, and shed forth their tears as the rain upon the mountains?
29 And Enoch said unto the Lord: How is it that thou canst weep, seeing thou art holy, and from all eternity to all eternity?
30 And were it possible that man could number the particles of the earth, yea, millions of earths like this, it would not be a beginning to the number of thy creations; and thy curtains are stretched out still; and yet thou art there, and thy bosom is there; and also thou art just; thou art merciful and kind forever;
31 And thou hast taken Zion to thine own bosom, from all thy creations, from all eternity to all eternity; and naught but peace, justice, and truth is the habitation of thy throne; and mercy shall go before thy face and have no end; how is it thou canst weep?
32 The Lord said unto Enoch: Behold these thy brethren; they are the workmanship of mine own hands, and I gave unto them their knowledge, in the day I created them; and in the Garden of Eden, gave I unto man his agency;
33 And unto thy brethren have I said, and also given commandment, that they should love one another, and that they should choose me, their Father; but behold, they are without affection, and they hate their own blood;
34 And the fire of mine indignation is kindled against them; and in my hot displeasure will I send in the floods upon them, for my fierce anger is kindled against them.
35 Behold, I am God; Man of Holiness is my name; Man of Counsel is my name; and Endless and Eternal is my name, also. 36 Wherefore, I can stretch forth mine hands and hold all the creations which I have made; and mine eye can pierce them also, and among all the workmanship of mine hands there has not been so great wickedness as among thy brethren.
37 But behold, their sins shall be upon the heads of their fathers; Satan shall be their father, and misery shall be their doom; and the whole heavens shall weep over them, even all the workmanship of mine hands; wherefore should not the heavens weep, seeing these shall suffer?
38 But behold, these which thine eyes are upon shall perish in the floods; and behold, I will shut them up; a prison have I prepared for them.
39 And That which I have chosen hath pled before my face. Wherefore, he suffereth for their sins; inasmuch as they will repent in the day that my Chosen shall return unto me, and until that day they shall be in torment;
40 Wherefore, for this shall the heavens weep, yea, and all the workmanship of mine hands.
41 And it came to pass that the Lord spake unto Enoch, and told Enoch all the doings of the children of men; wherefore Enoch knew, and looked upon their wickedness, and their misery, and wept and stretched forth his arms, and his heart swelled wide as eternity; and his bowels yearned; and all eternity shook.
42 And Enoch also saw Noah, and his family; that the posterity of all the sons of Noah should be saved with a temporal salvation;
43 Wherefore Enoch saw that Noah built an ark; and that the Lord smiled upon it, and held it in his own hand; but upon the residue of the wicked the floods came and swallowed them up.
44 And as Enoch saw this, he had bitterness of soul, and wept over his brethren, and said unto the heavens: I will refuse to be comforted; but the Lord said unto Enoch: Lift up your heart, and be glad; and look.
45 And it came to pass that Enoch looked; and from Noah, he beheld all the families of the earth; and he cried unto the Lord, saying: When shall the day of the Lord come? When shall the blood of the Righteous be shed, that all they that mourn may be sanctified and have eternal life?
46 And the Lord said: It shall be in the meridian of time, in the days of wickedness and vengeance.
47 And behold, Enoch saw the day of the coming of the Son of Man, even in the flesh; and his soul rejoiced, saying: The Righteous is lifted up, and the Lamb is slain from the foundation of the world; and through faith I am in the bosom of the Father, and behold, Zion is with me. (Moses 7)
Enoch was surprised to see that, in spite of God’s knowledge of all things, he wept in response to the behavior of others in a given moment. But, once God showed Enoch why he felt the way he did, Enoch felt the same way.
Interestingly, the way Enoch escaped from the sorrow of this exchange was through seeing (in the future) the coming of the Son of Man. The key way God helps us endure hard things is by showing us why they are worth it. This requires trust in God.
Having all things before you doesn’t mean you aren’t affected by present events. It simply provides you with tools to contend with them.
Being affected isn’t the same as being overcome. The Lord has overcome all things, but he is still affected by them. There are many things on this earth that cause great sorrow for the Lord, and there are many things that cause great joy. However, none of these things have power to overcome his character. Nothing will change what he does or why he does it.