It's the double-edged sword of regular exercise. When things are going normal it's easy to go back to the gym because you have a strong mental/physical baseline. Once things get out of sync (illness, vacation, etc.), you are in a completely different mental state and you just don't feel like yourself (motivation, etc.). Kind of an "objects at rest/motion tend to stay at/in rest/motion" scenario. Maybe just try not putting pressure on yourself to have a hard workout and instead go for lower weight just to get that feeling of exercise back? Set easily attainable workout goals as you ease yourself back into it.
Good post.
What saved me was changing my mindset to "what is going to make me happy". Everyone wants to look like some Hollywood actor, but to achieve that physique you're going to have to put a lot of work in and be on a pretty particular diet. If that's happiness to someone, awesome, but for most it's not. This is why I stopped focusing on weight. I focus more on looks and clothing size. However, I have no desire to eat perfectly clean, but I don't want to be an unhealthy fat, out of shape slob either. So I found a middle ground where I'm happy.
As far as going back to the gym. I think the other thing that helped me is figuring out what I enjoyed doing. When I was focusing on cardio, I ****ing hated it. It made me not want to go. I found things I liked doing to replace running. I enjoy swimming and doing the row machine so I have cut out all running. You also have to factor in life in general. If I was single, I'd go to the gym every day for at least 1 hour because I love lifting weights. However, having a family makes that very difficult. I tried going after work, but with kids soccer practice, homework, etc.. it was very inconsistent, which really killed my motivation. Now I just go on my lunch break about 4 days a week. It's only 30 minute workouts, but I enjoy them, and I can routinely do it. Wish I had more time, but it's been amazing for my overall health. Anyway, I think it's important to find something you really enjoy doing as opposed to something you need to do.