A good way to know if you are running out of steam is to estimate your average $ per card. This is an idea that came from my friend hggc on Isotropic first, and I haven't seen people talk about it much - but here's a good way to keep track if you need some more $ or you should keep race for VP:

* Basic Premise

- Each card is given an estimated value in terms of $. For the trivial example, Copper is 1, Estate is 0.

- Your initial deck has 7 Copper and 3 Estate. So a random card from the deck has average value of 7/10 = 0.7.

- When you buy a silver (which has a value of 2), random card from the deck now has average value of 9/11 = 0.82

This can be hard to keep track, but for this technique to provide some value, you only need to keep track of

1) An estimated running total of $ - start with 7, silver +2, gold +3, festival +2, for example

2) An estimated # of cards - easier on isotropic where you are fed these numbers, in real life you can get a good feel for it when you handle cards and shuffle. You can also get a sense of this by the # of turn since you probably gained 1 card per turn, and guess some amount of adjustment with curse / trashing / multi-buy.

* What about cards with +Card?

Suppose I bought 3 silvers and 2 gold since my initial deck. Now my average card value is $7*1 + $2*2 + $3*2 / 15 = $17/15 = $1.13

Say I bought a Smithy next. Smithy, when played, basically turns into 3 Cards, which can be estimated to be $1.13 * 3 = $3.4

Or if you bought a Peddler - that would yield you $1 and 1 card when played, which can be estimated to $1 + $1.13 = $2.24

There is the issue of playing +Card that draws into other +Card that you can't play because you're out of action. All I would suggest here is do your best to maintain a good ratio of Action and +Card, and overtime you can develop an intuition on how much to discount the estimated value from +Card.

Cards like Warehouse also requires a good deal of intuition to figure out an estimated value. The additional 3 Cards is easy to figure out (like Smithy), but you will have to also estimate the value of the 3 least valuable card in your entire hand. I don't have a good way of explaining of my thought process during a game, but when I do I'll add it to part of a larger post on this topic.

* What about cards with +Buy?

This is sort of outside the scope of avoiding "run out of steam" in a province race, but if you want, you can keep a running tally of +Buy you have in the entire deck and estimate the total # of +Buys per hand. This will come in handy when you are battling for the tiebreaking VP.

* What about cards with +Action?

If they don't provide $, they are not worth anything in this avg. value per card estimation. Beginners could benefit from this realization and see why overstocking on villages is generally a losing strategy. Unused actions at the end of a turn is like leaving money on the table. Imagine what you can buy instead if each action is converted to $1.

* What about special attack cards or cards like Minion, KC

They each need their own simplification to be accounted for in a manageable yet still useful manner. During game I can get some very rough intuition for how much they are worth in my given deck, but I have no idea how to explain here. When I do, I will attempt to write a larger post with that information.

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So now, to apply this estimated value - let's look at the simple example earlier, where you picked up 3 silvers and 2 gold, reaching an average card value of $1.13. Drawing a hand of 5 will yield $1.13 * 5 = $5.65 (I'm drawing with replacement here to simplify the math), which tells me that MOST of the time I wouldn't be able to buy a Province, but I can likely afford a Duchy on most turns and sometimes Gold.

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There are a lot more ways to apply this general "estimated card value" accounting that one can do in his or her head, and while it has served me well during games (I was at Level 35-36 before the 30 day cutoff kicked in), I am still working on ways to better presenting and explaining how to apply the strategy. But I hope this helps! And as for the experienced players, please give me your thoughts or criticisms on this technique!