Which currency (crypto & fiat) to use to measure profits? Lets say you have added enough USD to trade with so you pick BTC to trade altcoins with. 


You buy Altcoin X for let's say order total 0.5 BTC
BTC goes up in value but Altcoin X in USD has jumped big time in value
In BTC terms you have lost as BTC's value increase is more than Altcoin X 
You sell Altcoin X but you get less BTC, in USD terms you happy, profit both up
BTC drops in value to the USD, you got less than you started with now what?


Do you ignore the USD value and measure only in BTC to get your base currency/crypto currency to use for measuring profits trading Altcoins?

I just cannot get my head around it. Any advice and help/direction will be appreciated.
Companies measure their profits in currencies in which they keep the accounting. 
In my opinion regular people should measure profits in currency which they earn and/or spend. Therefore you should ask yourself: Do you spend BTC? Do you spend USD? 
You should measure profits in currency you can relate to in terms earning/spending money.