This information is included in my General Guide, but so many players have emailed me about their difficulty in sustaining their energy levels in the Mine that I thought it might merit a post.
The way to boost your Maximum Stamina and Fullness in IoH is by equipping Accessories made by Charlie. The best combination, in my own opinion is the Large Harvest Goddess Pendant and the Large Kappa Pendant.
I did not find the Earrings at any size to be particularly helpful. Yes, they will restore a tiny fraction of Stamina or Fullness or, in the case of the Witch Princess Earrings, both Stamina and Fullness, as time passes, but the amounts are not very significant. Of the three types of Earrings, the Large Witch Princess earrings probably are the most useful, but really not to the point of taking an equipment slot in place of a more desirable accessory such as the Turbo Shoes.
(With four equipment slots, equipping both Large Harvest Goddess Pendant and Large Kappa Pendant ALL THE TIME will give you only two free slots at any given time. I use the top slot for active equipment or Teleport Stone and keep the Turbo Shoes in the bottom slot, with the Large Harvest Goddess Pendant and Large Kappa Pendant to the left and right.)
In fact, initially I had hoped that the Large Witch Princess Pendant would be the equal of the combination of Large Harvest Goddess Pendant + Large Kappa Pendant, but this is far from the case. You do need to purchase it in order to unlock the Godhand but once purchased, I never used it. When equipped in the place either of the Large Harvest Goddess Pendant or the Large Kappa Pendant, it actually REDUCED total Stamina or Fullness. When equipped in place of BOTH, my total Stamina and Fullness both were reduced.
The Large Kappa Pendant and Large Harvest Goddess Pendant give you the maximum Stamina and Fullness capacity. Remember that, when equipped, they only increase the size of the Energy bars. They do not fill them with energy!
It is very important not to unequip either of these accidentally even for a moment as, when you do, your actual energy levels will disappear with the disappearance of the extra capacity. Re-equipping the accessory afterwards will increase capacity again but will not fill the bar!
In my General Guide, I explain how a player can equip both the Small and Medium Harvest Goddess Pendant to increase Stamina capacity until he/she is able to purchase the Large Harvest Goddess Pendant. The amounts of increased Stamina capacity given by each are added together to give you the largest capacity available until you are able to purchase the Large Harvest Goddess Pendant.
I find that increased Stamina capacity is far more vital than increased Fullness capacity in IoH. Fullness diminishes slowly as time passes. Stamina can diminish very quickly through use of tools or falling through pitfalls in the Mine.
Once you set 3 Green Wonderfuls in your Hammer and in your Hoe, mining itself no longer will use ANY Stamina, but falling through a pitfall still will decrease Stamina according to the number of floors through which you fall.
If you are not pressed for time (in real life), you can avoid pitfalls once your Hoe and Hammer can be used without decreasing your Stamina and go through the Mine solely through the stairs, but that really is time-consuming.
There is two situations when it may be to your advantage to go through the mine floor by floor, using only the stairs:
1. When you have reached Floor 50, and you still need Orichalc for Accessories. Once you have mined all the Orichalc on Floor 50, you may wish to use only the stairs to descend until you reach Floor 75. Between Floors 51-74, you should be able to find at least 1 Orichalc on each Floor.
If you have set Orange Wonderfuls in your Hammer and Hoe, the number of items you obtain each time you find a gem/ore, Black Grass/Lithograph is multiplied according to the number of Orange Wonderfuls in the Tool. The maximum appears to be 9, giving you 10 gems/ores each time you split a rock. Charlie will not allow me to set more than 9 in my Hammer, even though I have empty available slots.
As you usually are guaranteed at least 5 Orichalc on Floor 50 alone, and sometimes as many as 8, you can obtain 50 to 80 Orichalc in a single visit to Floor 50 with 9 Orange Wonderfuls in your Hammer. It is not as useful to set that many Orange Wonderfuls in your Hoe, but if you are at a point in the game where you have more Wonderfuls than you really need, by all means do so, making every strike for Black Grass one that nets you 10 Black Grass instead of 1.
Note that the same strategy can be used with respect to Adamantite. Find as many as possible on Floor 25. From Floors 51-74, Adamantite as well as Orichalc can be found on each of those floors, so if you use the stairs to mine on each floor, you should be able to find quite a few Adamantite for Makers, even if you have no Orange Wonderfuls in your Hammer.
2. When you have reached Floor 250. From that point onward, you can find EVERY special item in the rocks on each floor until you reach 255. To maximise the number of Mythic Stones, Orichalc, Pink Diamonds, Alexandrite and so on that you can take home from a single trip, you may wish to mine each of those floors.
Mining for Mythic Stone on Floor 100 should give you at least 5 and sometimes as many as 8. With 9 Orange Wonderfuls in your Hammer, you would obtain 50-80 from that Floor alone. From Floors 251-254, you should be able to find another 5 at least without any Orange Wonderfuls in the Hammer. That would give you another 50 with 9 Orange Wonderfuls in your Hammer.
This strategy makes it possible for you to obtain all Accessories as well as a Mythic Refrigerator as early as possible in the game.
It is useful with respect to obtaining the Adamantite needed for all Makers, although you may wish to have the Makers built BEFORE you have the opportunity to obtain more than one Orange Wonderful!