I strongly recommend generating a new wallet id (If the wallet software allows it) at the start of each month....and put the fiat investment amount in the wallet name. I add in money each week, then amend the name of the wallet. For example: 1706-100 means that I have invested GBP 100 in the month of June in 2017. My wallet tells me the latest price in GBP - so I can tell in an instant that what I invested in June is in profit. I see the wood through the trees, I can see instantly that it's only the last month or two that are in the red, while the rest are all in profit. It also helps keep me motivated to keep investing each week and each month.