Don't worry if you're starting a new training program and it seems easy.
Don't worry if you planned to train 4 days a week but only got 1 session done.
Don't worry if you aren't exhausted at the end of every session.
These things aren't indicative of your long term progress.
All good training plans start easy to allow you time to acclimatise to the work. If you can't recover from this session, then it has a detrimental effect on the next one.
If you start out training at your max, how are you going to beat that next time?
You're better off going a little easier and giving yourself a "run up" to smash through old plateus, rather than trying to batter them from where you are.
Very often by starting below our current max gives us a few weeks of gradually more intense work so that by the time we hit our perceived max, we smash through it without noticing.
This goes for coming back after a lay off too, or those with busy lives outside training. Many of the office crew that train with me have ridiculous workloads. if this eats into your recovery, then you must adapt the training, nutrition etc accordingly.
If that means you only get one session in this week, then be happy in the knowledge that you got one in. Over the next few weeks look to find time for the second, the third. If this means an earlier bed time and earlier rise to train in the morning, so be it. If it means shorter session that you can do on your lunchbreak, so be it. Maybe it means Grease The Groove style exercise breaks during very busy times.
If you're not in a pre event peaking cycle, then you are training for the long haul, and that is about consistently ticking the boxes, not killing yourself in an unsustainable manner.
Peaking cycles are deliberately hard, they leave an already well conditioned athlete tired but they are short, planned intense periods to put an edge onto an already sharp sword.
Most of the training building up to this looks a lot like the training the non athletes, the office crew and the mums & dads do.
So relax, you're in this for the long haul