1- Instead of feeling guilt, which is burdensome, try to feel excitement that you spent even a few minutes with your Lord. Yes, it’s our loss if we don’t spend enough time, but try not to feel burdened. This is one of the tactics of Shaytan to de-motivate us and deflate us from worshipping Allah. Even if you prayed the Shaf’ and Watr only, while lying down, just feel honored that you worshipped your Creator and connected to Him. When we pray less than the 11, one way to compensate for that is to increase the quality of the 3 that we are praying. Focus more. Make them from your heart more. The quality is more important than the quantity.
2- You can do Qadha’ of the 8 you missed. It’s highly recommended and carries a great reward. It’s best to do the Qadha’ during daylight, not at night.
3- Change the timing of when to pray. Pray a few rak’as before you sleep, then a few more before fajr (for example).