Sorry for a wall of text! Skip to the end for the tl;dr.

Although I'm pretty new to lifting (only started on a proper program in early March) so I should be able to lift way more, it seems that I'm mentally psyching myself out of mainly squats, but also maybe deadlifts. I'm lifting for my own enjoyment and fitness so my goals are just to get stronger really.

Here's the situation: My stats are 19/54kg (119lb). The other week I got sick (nothing too bad, just a common cold and a sore throat) so I took my lifts down a bit after I felt I was up for it. Before that point, I'd gotten to 62.5kg (138lb) on my squat. However, ever since then I haven't been able to even hit 60kg (132lb)!

Last week's workout I failed on 60x2 and took it down to 57.5x5 for a few sets, but today I could only get 60x1 before I failed. I think I'm psyching myself out at the thought of getting 20kg plates on the bar and I'm getting all caught up in my head. And today even the 55kg (121lb) felt like a bit of a struggle.

Also, for my deadlifts, I PR'd 72.5(160lb)x3 on Sunday but on the fourth rep it didn't budge at all! I think I ran out of steam but also psyched myself out with the thought of the weight. The only plus is that my bench is pretty solid.

Basically, I feel like I'm a failure because I can't even get higher than I was before. I'm not sure if it's because I've been a bit stressed out about uni study and assignment season. Since lifting is something that I'm doing for my own personal enjoyment, I know my priority is my own well-being and that I shouldn't get stressed out, but I can't help it - I'm so frustrated at myself. Please shoot any advice or suggestions my way! Should I consider changing my goals or program? Should I take it easier on lifts and just chill out?

tl;dr: got sick, can't lift as much as I could before, feeling frustrated. Any tips?