Thanks for sharing your lesson with us - we've all made this mistake many many times!
Now I didn't realize at the time that I should NOT have purchased ETH or BTC from Coinbase. Not only did they charge fees and I didn't get the best price based on bid/ask spread, but I could have just deposited via GDAX (and avoided the fees!
Just on this - I've been thinking the same lately but use Kraken so is it better for me to deposit on Kraken and buy ETH on there rather than coinbase? The spread + fees combined are very high on coinbase so I'd like to avoid this to maximise my gains!