I find it rewarding too to look at an end product I made, but I often lack motivation to actually get to that point. I've been working on my basement for the past years on and off. In reality I could have finished it much faster but I often don't have motivation to put in a full day of work and might only put a few hours or wait till it's late before I start. When I'm lying in bed or at work I have 110% motivation, but when I actually have the time, it's like meh, I rather sit, drink pop, and nef.
Though some days I will be on a roll and put in tons of hours. I want to build a shed this summer and because an outside project really depends on weather I will need to take full advantage of days where it's nice out, so hopefully I will get on a roll. There's no reason why I can't do it in like a week. I find if I really focus on the end product and give myself a daily goal it helps. Like when I was framing my basement I'd say "ok I need to finish at least till the end of this wall span" then I get to there and say "know what I'm just going to lay the bottom and top plate and get it ready for tomorrow" then if I'm on a roll I end up doing way more than I planned.
My newest hobby is electronics, I have not started that far into it yet - mostly watching videos and buying parts, but I plan to start getting into actual projects, so when I actually design a circuit board and have the end product in my hands with all the components on it, it will be quite rewarding to see it work. The nice thing with that particular hobby is that it has the potential of making me money, so it's something I need to look at too. If I can get good enough to make an actual product that performs a certain task and does it well, and sell it (and hope I don't get sued by a patent troll) then that will be super rewarding and something that will keep me motivated. Money is always a good motivator. But seriously, now is a better time than ever to get into electronics, with online ordering, online selling, etc. It was not this easy before.
Downside is depending on the nature of the product you're making it may have to be UL approved and so on, then that gets very hard to do as a 1 man low budget shop. And you have to compete with China, who does not actually need any UL approvals.