Trying to get motivated learning a new language

So I'm currently learning Japanese. I'm at the very beginner level learning the Hiragana. After that the Katakana follows and then Kanji.
I just received my study books I ordered for over 70 bucks last week. However, in order to progress and start with these study books, I need to learn the Hiragana and Katakane first(japanese syllables).

When I manage to start with learning, I usually do it for about an hour. However, there are often days where I just can't motivate myself doing anything regarding my learning goals.
It's kind of stupid to invest money into a project and then do nothing, I know.

Does anyone know a strategy to overcome this? For example, how do I learn even when I'm not feeling to do so? When I force myself it's hard to remember stuff afterwards. I try to follow my weekly plan, but sometimes that would force me to learn on a day on which I don't feel like learning. Without that weekly plan on the other side, I would do pretty much nothing productive at all.

You see, I need that weekly activity plan I'm having on my wall to get my structure and routine, but contrary if I force myself to learn at a certain time or certain day is not working so well for me either.

I'm in almost all life areas a very lazy person. I'm trying to change my life for the better, but it's so hard to stay with things longer than a few weeks.