I do several things to keep interest.
1. I have been working on this layout for many years and each area in in various stages from just a plain base to "finished" (hahah). That way when I go downstairs I can work on what I feel like that particular day. Benchwork, wiring, scenery, whatever. Then there is not the drudgery of having to complete step X when I really feel like doing step Y. I usually run at least one train round and round while working on the layout if possible.
2. All trains are put away on the layout. Engines parked, cars in yards and the mains clear. I challenged the kids when they were young to NEVER touch am engine or a car with your hand if you can help it. No 0-5-0. If you want to build a train then operate an engine, dig out the cars you want with the engine and build a train. Then run the train. But before Mom calls us for dinner... sometimes after dinner, you had the operate the train to put all the cars away and park the engine. This really became interesting when two kids wanted to build and run trains at the same time. They had to think, they had to cooperate and they had to share. More time was spent building and putting away than running in circles or even delivery and pick up of freight passengers. Every session was a little different depending on the train they wanted to build.
3. On the workbench. Lately, I've been getting a lot of satisfaction away from the layout and on the workbench either converting engines to battery power, custom painting cars or kitbashing structures. I find this work relaxing and fun.
Don't you need some new clothes darling?
4. Get away from the trains. It's healthy to have other interests. I fly model RC planes and in the nice weather, like to do outdoors things like camping. I have to do yardwork too... not a fan of that. So train time for me is typically when it is cold or rainy. As I get older, I much prefer Winter. No yardwork. Just grab a beer and head to the basement to work or play trains.
Take today for example. I got VERY excited because it was foggy and damp this morning. Looks like rain. I thought to myself, Yippi, I'm going to mess with that BL-2 today. I've been wanting to try my first attempt at fixed pilots.
But alas... It's going to be 91 and sunny today. I have to powerwash the deck, set up the outdoor furniture, wash the camper, wash the truck and time permitting, mow the lawn today or tomorrow. No trains today.
At least I had fun reading and talking about trains on OGR this morning with my cup of coffee.
Stay motivated.
Ron