You'll have heard me say it before... to be motivated you have to be interested, passionate, or receiving a reward from something.
Having said this, motivation will still come and go.
There are two things that hold you together when motivation won't: habits and discipline.
Habits: Read the book Atomic Habits. Honestly, just do it. Go and order the book or audiobook, get stuck in, and thank me later.
Discipline: An area where I have my own thoughts to share... it starts with self-awareness, and is something that can be learned and must be practiced.
Nobody is going to teach you your strengths, weaknesses, and limits. You have to learn them yourself. As you become more familiar with these, you can start to build up a picture of the lifestyle that you can sustain - which also exploits your uniqueness and traits, and aligns with your goals (which must be crystal clear).
You must also remove the fear of failure, and the need for perfection. You will not get things right the first time round, and there will never be a perfect moment... for anything. This loosens the ties that often pin us down, and allows us to seek consistency without the over-riding guilt that makes us drop things altogether.
Two key points there that ALLOW you to be disciplined: sustainability and consistency. Put too much on your shoulders and you'll drop the lot. Instead, be self-aware enough to know just the right amount of weight that you can carry the whole way.
Finally, give yourself a break. I mean it. By simply signing up to this email newsletter and getting this far into the issue, you're taking steps towards a healthier happier you. Cutting yourself some slack and enjoying the process will always yield greater rewards, in all areas of life.