Isak's match fitness remains lacking and has left new Sweden coach Graham Potter unable to consider him for back-to-back World Cup qualifiers this week.
"It's always frustrating when you're injured. Regardless of whether it's one match or more. It's always worst for the player himself," Isak told Sportbladet.
"It hasn't been optimal. But when I'm on the field, I don't give myself any excuses. I always want to play my game and perform. But yes, it's hard to be away and not be able to help and contribute. Now I'm back and I'm positive."
Isak added, "There is not much that is easy in football. But with experience you learn to handle things. That's how it is with injuries and everything like that. You learn to handle it and get back in the right way."