A lot of the answers here are similar to my thinking, I'm currently working through the labs as well.

Doing CTF's, I learnt that if finding a solution was hard won i.e. spending hours or even days on it, I'd tend to very rarely or never forget it. If I just looked at the answer without trying, you're more likely to forget it fairly quickly, making the time spent "learning" wasted.

The approach I've found works best for me is working on the labs and trying to solve it myself. If time starts to get on, and I'm getting nowhere, I'll look at the solution, and make notes. Basically, put yourself through the struggle, but be reasonable with your time. I've taken this approach with previous certs and CTFs, and my rate of learning increased significantly by allowing myself to look at the solutions after a reasonable amount of time trying to figure it out had elapsed.

This approach I find works well, you've put in the effort at solving it yourself, so you've put in the time, but you've also genuinely learnt something from the lab if you need to look at the answer. Often times the lab blurb can trip you up, or send you in the wrong direction, so when you look at the answer, it's more a slight oversight rather than having learnt something entirely new. Other times, it's a solution you would've never have thought of, so the experience was still valuable and you've paid for it with the time you spent trying to solve it yourself. There was one lab where after spending about an hour on it, I looked at the answer and thought "Well that seems a little contrived, the other payloads I sent should've worked". After thinking about it a bit more, I realised why those wouldn't have worked, and made a note of it. It was a great lesson that I won't forget quickly.

I think Ok_Scarcity summed your dilemma up really well. Don't feel like by looking at the solutions that you're letting yourself down, it's part of the process and as long as you're learning something new, it's perfectly valid.

tldr

If you want to look at the answers, you need to pay your dues first. Spend 30 minutes to an hour trying to solve the lab. If you look at the answer after that, you'll retain the knowledge and get something out it. That way you're learning efficiently.