The midfielder moved to the Estadio Benito Villamarin on loan from Barcelona in January and hasn't quite hit the heights he would've hoped for.
"[It was going] quite well in the first few games, I was playing well," Alena told Betis' radio station.
"After that, I have to give my own account - I don't think I've been the player that I am.
"I have to improve for the trust that's been placed in me and for where I've come from.
"This break has served me well to relax my mind.
"It's not easy when you're in one place for your whole life and suddenly you change place, playing style, system...
"I'm not making excuses, but I know that I have to give a bit more of me.
"I don't think it's a playing problem, but more of taking more risks.
"You want to do everything well and when you do everything flat, sometimes that's not the right way.
"I have to do that and I'm hungry to make that step forwards and be the true Alena that I was when I was at Barcelona and when I had confidence.
"I trusted my teammates and they trusted me, and I hope to be able to change the picture."
Alena didn't rule out making his stay in Seville permanent once his loan expires.
"It would be crazy to close the door on Betis," he said.
"I'm very happy [here], I love the city, I've had my first child here and I'm delighted at how the club treat their players."