I don't think there's anything wrong with monitoring capital value. Obviously, if you're doing it five times a day, this approach may not be for you.
I've heard many people here claim that they topslice, move stops, rebalance, cut losses, etc, even though they're dividend stalwarts at heart. You can't really do that unless you know what the score is.
It really just comes down to self-discipline. If you're going to panic out of a position when a holding slumps 20% in a month, time to step away from the screen.
I got involved in managing my own investments because I wanted lower costs and complete control. Prior to that, it took ages to get a simple quote of overall book value, and an unbelievable ten working days for an encashment - which was invariably not conducted with my personal tax efficiency in mind. And I was paying for this privileged treatment.
Now I can fire up the spreadsheet at any time and see capital appreciation, current yield, yield on cost, buy/sell flags of my choice, etc, per stock and per asset class. And I can buy or sell in five minutes flat.
Just because I now have this degree of monitoring and control doesn't mean I'm glued to the pf or constantly fiddling with it. I've seen it down and I've seen it up, but as an accumulative reinvestor, months go by without me buying or selling a solitary sausage.
If you have the right temperament, monitoring can actually be a useful reinforcement mechanism. You get to see that even blue chips swing around quite alarmingly at macro whims over time and learn not to take the swings too seriously.
Buy and hold doesn't mean buy and ignore.
Incidentally, I find it useful to regard the bottom-line capital appreciation in terms of x years of inflation. Aiming to stay a few years ahead on that basis while working on sustainable yield gives me a solid strategic focus.
Ah, tactics and strategy. Every investor should play chess...