I can't do without caffeine I never feel like it massively increases my energy or makes me feel I can do more, but I feel so, so, so much worse in all ways but especially cognitively if I try and cut it out. My activity level remains the same whether I am having caffeine or not, but how unwell and mentally sluggish I feel increases massively if I try and cut it out. I wouldn't say I think caffeine in any form makes me feel stimulated either, just more able to resolve that sluggish feeling in my head and body. My limits remain the same but I feel better within them.
I've tried Cutting caffeine several times in the past thinking I'd be being healthier and feel better for it when I've felt especially tired and had more headaches etc. because I was wondering if I'd fallen into a caffeine cycle and that was why those symptoms increased. But when I cut it out I didn't feel any better and I felt so much worse in all ways; I even slept worse, and felt even worse than usual on waking! It was like caffeine withdrawal that just didn't end. I held out for a couple of months each time I tried thinking this would resolve and it didn't. My brain felt sluggish, I just felt even more fatigue than usual and other symptoms increased too.
I usually have a couple of cups of coffee when I wake and then maybe a couple of cups throughout the day, I tend to respond to the feeling if I need a boost and just have a cup of coffee or tea as an when I want one without bothering about it anymore. My energy pattern is more like roller coaster, with peaks and troughs through the day or my waking period, than a curve and I find that if I take a cup of coffee sometimes my energy Level doesn't increase but it feels more stable over the day unless I've had to over exert Or I'm in a crash when I can't control the steepness of the dips in energy; then I
definitely feel better if I have a cup When I feel I need it. I've also found some evenings that if I have a cup of coffee in the evenings I feel like I sleep better. I certainly don't sleep any worse for it! So at worst it doesn't seem to negatively influence symptoms and at best I feel a lot better for it. So I don't fret about caffeine at all tbh.
I always find this one really interesting with how some people feel better for it and others don't.