When the market reaches a significant level in our favor, I feel that it's time for it to reverse and go down—even without any specific signals.
Conversely, when the market keeps declining, and I anticipate further drops, I still can't resist opening a long position. It's not a regular occurrence, but when it does happen, I end up suffering losses.
Both of these can be prevented :
by having extra asset at hand for the first one and extra fiat at hand for the second one.
But this is tricky and it is tough in the beginning you might feel lost at the sea of numbers and charts. But as you get the feel of the market, it starts becoming second nature to you.
Your target should be to keep buying when the market is dropping till you spend you allotted budget. How much? This will vary, but you will be able to estimate a budget depending on your own leverage.