In General:
This deck should be played patiently. Just give your opponent time to build up his winning option, then destroy everything and start the real play. Means, try to get "Solemnity" on the table as soon as you can. You will disable a lot of deck types, ideally at your third turn.

Next you should use "Ritual of Rejuvenation" as often as you can for drawing cards. And gain life, so rush decks have a harder time with you. In Mid-Game you should throw out some creatures that are just in the deck for keeping your opponent busy and decrease the chance that he has removals or counter spells if the important stuff is coming up.
Also a "Protection of Hekma" is always a good idea, to break 1/1 Token decks and just not loosing life to fast.

4x "Invoke the Divine" are always good. But in best case you use it before the block-step to free up creatures from any kind of Cage-Spell (like "Ixalan's Binding" or "Cast Out").
 
With "Hour of Revelation" or "Dusk / Dawn" you may clear the board if your opponent is too fast or is becoming a threat. Remember that you just have two "Oketra's Last Mercy" in your deck. The only creature in your deck for winning this game is the "Seraph of Suns". It's not the best creature, and very expansive. BUT, if you did everything right, your opponent is almost played out because you destroyed his winning options several times.

So the Seraph should have an easy time. Because of "indestructable" he survives most of the time. And "Flying" gives you a good chance to be in the position where you can ignore grounded blockers. 



Psychologic:
The fact that you will generate life is made for aggro and weenie decks. You just need to survive long enough until you play one of the fake creatures like "Crested Sunmare" or "Lyra Dawnbringer" these creatures are inside the deck to keep your opponent busy and catch counter/direct damage - Spells. Or to block small crowds.

But "Evra. Halcyon Witness" is a card, that lets your opponent think you will make yourself life, to push Evra. Making it the most dangerous creature in the deck. But again, it is just fake for catching spells or "sacrifices".

The "Sheltering Light" should only be used on creatures. And only for these, that have to much impact on your gameplay. Killing attackers with "Bright Reprisal" will lead to the point, where your opponent doesn't attack sometimes if you have untapped lands.. Its also more for psychological reasons, not treated as a real removal. (but works in both ways.)

2x "Adamantine Will" are there for two reasons. First: Let your enemy think, that you might have it on your hand and stop attacking if you have a simple blocker. Second: Prevent a creature, if you wipe the board again with "Hour of Revelation". 

"Overwhelming Splendor" can be used to check if your enemy still has counter spells on his hands. If not, you can start. If you bring it on the table, mostly the opponent concede the game at this point.


Loosing:
The biggest threads for this decks are green dinosaur decks that are well constructed. Finding yourself in Turn 6 with an opponent that brings up one 4/4(+) creature after another without having a mass removal in your hand is probatly the worst situation. Also Spore-Decks that are not based on counters can be dangerous.
Basicly every Deck that has more then 2 options to destroy enchatments can be harmfull.

Intention:
This is kinda a control deck. The intention behind it is, to make the opponent think that he have the lead. Hes the big boy and you just dont have luck with your drawings or you have a bad deck. You dont to much. Rarely you play a creature that he will kill instantly, you make yourself life, but dont have any kind of defense. So will start to use gamechanging-spells earlyer and dont waits for the best moment. Let him know: "Hey mate, you are the BOSS, you defeat me with ease! Do it!" If that process is running, destroy everything, multiple times. Then, if all good cards of his deck are played, start with your own cards.