Hi guys, i have a question...

I am a uk user and im registered with Gdax and Bittrex.

I buy my Bitcoin at GDAX, and sometimes i like to hold Alt-Coins over at Bittrex.

Now my worry is this... (i have ignored fees and actual growth/retreat levels to make it simple)

Suppose i have $1000 to invest in Alt-coins and the price of Bitcoin is $10,000 and i buy 0.1 bitcoin ($1000)

Lets suppose i invest that amount in Alt-Coins and the Alt-coins grow by 50% so now my $1000 has grown to $2000 in Cryptos. Fantastic.

I sell my Alt-Coins for Bitcoin and i want to cash out the Bitcoin back into Fiat so i can see $2000 in my Bank Account...

But lets say the price of Bitcoin falls to $5000.

My $2000 will shrink to $1000 regardless of how well my Alt-coins performed, because now 0.1 of Bitcoin = $500  

I know 50% may be a extreme exmaple, but the point holds that even if Bitcoin goes down 10%, my Bitcoin is worth less and hence the only
way for me to actually gain wealth is for both Bitcoin and the Alt-Coins to go up together (or for Bitcoin to stay stable and for the alt-coin to go up).

If i have misunderstood please explain, and what do you think about this?