In terms of how I felt when I first put money into investments, I had also read the books and advice about treating it like a long term game, don't fret the short term drops and variations and it will all work out in the long term. That said, I would still log into the broker site too often to check what the balance was and how they were doing, and when it was down, it was hard often to be as objective as I had told myself I was going to be.
Are you able to save and invest regularly, a fair amount every month? What I do now is keep a simple net worth spreadsheet that I update about once a month after payday. Since I am saving and investing a good chunk of every paycheck, that net worth goes up pretty much every month, which makes it easier to not worry too much about the investments going down a bit. If I am going to graph something, that's what I will graph to make myself feel good about how we are progressing.
I think making regular contributions to your investments will also help. If your habit is just to put x% of your paycheck into your investment account every month, then when the market takes a hit and drops it's easier to say, "ooo, market's on sale!" and congratulate yourself for getting more value from your monthly $y when you make your regular investment. If you contribute irregularly, then you may be more likely at that point to say "oh my, the market is dropping, maybe I should hold off and wait to see how this is going to turn out," and end up not buying when the market is cheap.