I just chalk this up to fundamental differences in Hikari and Yuu's worldview. Yuu is the type of person to quickly come to a negative decision (even if it ends up being the right decision - we've gone over whether or not he should have confessed to Hikari in middle school and it was proven that he would have most likely failed based on Hikari's inner thoughts) whereas Hikari is full of hope and continues to try.
It's not about "quickly giving up" and "trying", at least not in this case.
Look at it this way: Yuu needs to beat the national record in running, while Hikari needs to run 100m in 14s. Yuu realizes it's impossible for him, still takes a long training camp as his last attempt, tries to beat the record and fails. Hikari thinks she isn't quite there, but she still believes it's possible, so she starts training and attempting to reach that result.
Did they ever explain why Hikari and Yuu don't hang out as much at Yuu's house during the three years of middle school?
No. But I think it's just a normal boys and girls thing, just a stage when boys are embarassed to spend time with girls because it's uncool and vice versa.
Also, I chalked Hikari's attitude as this: It's not that she doesn't care he's not going to her high school - she considers them close friends so even with them going to different schools she can still see him everyday as they are next door neighbors. I think this is more of Hikari being a golden retriever whereas Yuu is instantly going into worst case scenario mode.
@story645 made this argument too. But:
- They were not even hanging out at each other's houses in middle school
- Them going separate ways means the distance increasing even further: different groups of friends, different interests etc.
And Hikari saying that she spent more time with her friends than with him during that summer break in 2nd year HS confirms it: even though she is already in love with him, she now has her own group of friends, where Yuu doesn't belong, and she is spending more time with them than with him. So they didn't drift apart only because she fell in love with him and he wasn't averse to her trying to close the distance.
I'm baffled seeing that any series gets this many comments
Well, this "chapter" is an exception because we're on 2 months break and there were some WN extra chapters released, which we're discussing here in the latest manga chapter thread. But still yes, some of the older chapter did get a lot of comments too.