The Brazilian was shipped to Portugal after falling down the pecking order under David Moyes.
"On one hand, I'm sad to not be able to help the team as [much] as I would like," Anderson told talkSPORT.
On another hand, I'm happy to have a great opportunity to be very motivated and display my football playing for Porto; it is a great opportunity for me.
"Yes [I am disappointed] because when I come here I had a goal.
"Everything changes, this (coronavirus) as well, I lost my space at the club and I know I have a lot to show.
"I think it was the right decision for both sides for now. I have a contract with West Ham still and I need to do my best to be back stronger.
"I have in my head still two years or more with West Ham. This season didn't start the way I wanted to start playing and helping the team.
"That is difficult to say [why it didn't go my way] because I am motivated, the team now is going great. I just want to play and this was a great opportunity."