Many years ago I told myselfsaid I was going to improve my Japanese. Many years ago I said I was going to improve my Japanese.

"I told myself to" is a very uncommon way of phrasing this kind of sentence.

I musthad to write a diary every single day and post it on this website. I had to write a diary every single day and post it on this website.

If I didn’t post because theof laziness I willould feel guilty. If I didn’t post because of laziness I would feel guilty.

So, I told myself to just writing something, all I need ied was quantity not quality. So, I told myself to just writing something, all I needed was quantity not quality.

AtIn the end, I did keep this promise, at least until now. In the end, I did keep this promise, at least until now.

But recently I didhave been writeing less than before. But recently I have been writing less than before.

That is nNot because of the laziness. Not because of the laziness.

That isBut because I amhave been able to find a new way to improve my Japanese. But because I have been able to find a new way to improve my Japanese.

So, now I dido write less, but at the same I did “talk more”, and “interactive more”. So, now I do write less, but at the same I “talk more”, and “interact more”.

Now, even though I am writing less but, I feel a lot more happier. Now, even though I am writing less, I feel a lot happier.

Avoid using "more + [adjective]-er" expressions. They're unnatural English. "More happy" or "happier" are acceptable, "more happier" is not.