I'm a relatively new PhD student, and I'm faced with a new (for me) situation. Before, I always had grades and the likes to tell me how good or bad I was doing: if I was at or near the top/bottom of my class, if I passed my exams or not... were all more-or-less objective indicators to tell me how I was doing.
But now that I've started to do research, I have none of that anymore, and it's quite discouraging. It's not that I need constant validation to boost my self-esteem, but rather I'm afraid that I'm not working hard enough, not learning enough... and that it's all going to crash down on me at the end ("welp, your funding has run out and you've produced nothing good enough, no PhD for you"). I sometimes find results, but they always feel rather insignificant. And the fact that I used to be good as a student whose only job was to learn about well-established topics from good professors doesn't mean I'm good enough at research, either.
I've read several Q&A's here (How should I deal with discouragement as a graduate student?, “I've somehow convinced everyone that I'm actually good at this” - how to effectively deal with Imposter Syndrome) and they've been helpful, but simply telling myself that maybe it's just the impostor syndrome talking isn't helpful – maybe I'm really an impostor, too...
Of couse I can ask my advisor from time to time, but if I start asking every month I don't think he's going to appreciate it, and if I ask that bluntly he may not want to hurt my feelings and tell me the truth. So how do I, a PhD student, can evaluate how well I'm doing?