Blackjack is a high variance game. That means you can be way up or way down (or anywhere in between) over the short run. However, the house has an edge when you’re just playing basic strategy. So, in the long run, the house always wins. The longer you play, the more certain your outcome. Playing everyday for a year is enough to reach the long run. So you’ll be down with almost 100% certainty.
It is easy to calculate how much you can expect to be down. Just multiply three things together: the house edge, your average bet size, and how many hands you play. For example, say the house edge is 0.5% (which would be a typical game), you always bet $10, you play 100 hands per hour on average, and you play 6 hours a day for 365 days. So, you can expect to be down about $10,950.
If you want to have a positive expectation, you need to do something to move the edge in your favor like by card counting.